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 $61.28   10.674%   $67.821   $67.82   $67.80   $67.80  
  Purchase #2 $143.93   5.311%   $151.5741   $151.57   $151.55   $151.60  
  Purchase #3 $194.76   9.461%   $213.1862   $213.19   $213.20   $213.20  
  Purchase #4 $83.58   5.665%   $88.3148   $88.31   $88.30   $88.30  
  Purchase #5 $235.60   11.801%   $263.4032   $263.40   $263.40   $263.40  
  Purchase #6 $125.52   3.793%   $130.281   $130.28   $130.30   $130.30  
  Purchase #7 $16.29   11.645%   $18.187   $18.19   $18.20   $18.20  
  7 purchase totals = $860.96       $932.7673   $932.76   $932.75   $932.80