Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $207.92   4.737%   $217.7692   $217.77   $217.75   $217.80  
  Purchase #2 $245.58   11.804%   $274.5683   $274.57   $274.55   $274.60  
  Purchase #3 $242.86   11.861%   $271.6656   $271.67   $271.65   $271.70  
  Purchase #4 $213.91   12.497%   $240.6423   $240.64   $240.65   $240.60  
  Purchase #5 $167.50   5.492%   $176.6991   $176.70   $176.70   $176.70  
  Purchase #6 $191.72   5.584%   $202.4256   $202.43   $202.45   $202.40  
  Purchase #7 $147.47   10.736%   $163.3024   $163.30   $163.30   $163.30  
  7 purchase totals = $1,416.96       $1,547.0725   $1,547.08   $1,547.05   $1,547.10