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 $151.82   10.629%   $167.9569   $167.96   $167.95   $168.00  
  Purchase #2 $184.84   11.145%   $205.4404   $205.44   $205.45   $205.40  
  Purchase #3 $26.76   3.468%   $27.688   $27.69   $27.70   $27.70  
  Purchase #4 $218.90   8.873%   $238.323   $238.32   $238.30   $238.30  
  Purchase #5 $105.26   7.689%   $113.3534   $113.35   $113.35   $113.40  
  Purchase #6 $68.39   8.361%   $74.1081   $74.11   $74.10   $74.10  
  Purchase #7 $61.32   12.214%   $68.8096   $68.81   $68.80   $68.80  
  7 purchase totals = $817.29       $895.6794   $895.68   $895.65   $895.70