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 $66.95   13.501%   $75.9889   $75.99   $76.00   $76.00  
  Purchase #2 $148.68   11.781%   $166.196   $166.20   $166.20   $166.20  
  Purchase #3 $187.81   7.246%   $201.4187   $201.42   $201.40   $201.40  
  Purchase #4 $160.74   13.650%   $182.681   $182.68   $182.70   $182.70  
  Purchase #5 $11.44   4.747%   $11.9831   $11.98   $12.00   $12.00  
  Purchase #6 $219.46   13.639%   $249.3921   $249.39   $249.40   $249.40  
  Purchase #7 $29.52   11.656%   $32.9609   $32.96   $32.95   $33.00  
  7 purchase totals = $824.60       $920.6207   $920.62   $920.65   $920.70