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 $213.50   9.438%   $233.6501   $233.65   $233.65   $233.70  
  Purchase #2 $196.73   11.583%   $219.5172   $219.52   $219.50   $219.50  
  Purchase #3 $66.64   8.568%   $72.3497   $72.35   $72.35   $72.30  
  Purchase #4 $232.84   3.311%   $240.5493   $240.55   $240.55   $240.50  
  Purchase #5 $237.47   8.792%   $258.3484   $258.35   $258.35   $258.30  
  Purchase #6 $5.53   8.714%   $6.0119   $6.01   $6.00   $6.00  
  Purchase #7 $116.25   11.505%   $129.6246   $129.62   $129.60   $129.60  
  7 purchase totals = $1,068.96       $1,160.0512   $1,160.05   $1,160.00   $1,159.90