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 $71.52   5.343%   $75.3413   $75.34   $75.35   $75.30  
  Purchase #2 $74.83   9.527%   $81.9591   $81.96   $81.95   $82.00  
  Purchase #3 $96.61   9.411%   $105.702   $105.70   $105.70   $105.70  
  Purchase #4 $192.37   7.768%   $207.3133   $207.31   $207.30   $207.30  
  Purchase #5 $94.38   13.613%   $107.2279   $107.23   $107.25   $107.20  
  Purchase #6 $178.25   9.537%   $195.2497   $195.25   $195.25   $195.20  
  Purchase #7 $163.82   11.437%   $182.5561   $182.56   $182.55   $182.60  
  7 purchase totals = $871.78       $955.3494   $955.35   $955.35   $955.30