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 $89.91   5.640%   $94.9809   $94.98   $95.00   $95.00  
  Purchase #2 $84.77   5.407%   $89.3535   $89.35   $89.35   $89.40  
  Purchase #3 $108.87   9.819%   $119.5599   $119.56   $119.55   $119.60  
  Purchase #4 $134.54   12.606%   $151.5001   $151.50   $151.50   $151.50  
  Purchase #5 $169.51   8.469%   $183.8658   $183.87   $183.85   $183.90  
  Purchase #6 $243.41   5.603%   $257.0483   $257.05   $257.05   $257.00  
  Purchase #7 $16.67   3.665%   $17.281   $17.28   $17.30   $17.30  
  7 purchase totals = $847.68       $913.5895   $913.59   $913.60   $913.70