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 $88.75   7.166%   $95.1098   $95.11   $95.10   $95.10  
  Purchase #2 $60.84   3.199%   $62.7863   $62.79   $62.80   $62.80  
  Purchase #3 $70.44   3.766%   $73.0928   $73.09   $73.10   $73.10  
  Purchase #4 $148.61   4.540%   $155.3569   $155.36   $155.35   $155.40  
  Purchase #5 $16.94   7.266%   $18.1709   $18.17   $18.15   $18.20  
  Purchase #6 $210.33   5.116%   $221.0905   $221.09   $221.10   $221.10  
  Purchase #7 $130.28   5.696%   $137.7007   $137.70   $137.70   $137.70  
  7 purchase totals = $726.19       $763.3079   $763.31   $763.30   $763.40