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 $176.43   10.628%   $195.181   $195.18   $195.20   $195.20  
  Purchase #2 $182.52   10.110%   $200.9728   $200.97   $200.95   $201.00  
  Purchase #3 $174.27   5.447%   $183.7625   $183.76   $183.75   $183.80  
  Purchase #4 $44.59   3.747%   $46.2608   $46.26   $46.25   $46.30  
  Purchase #5 $169.65   13.210%   $192.0608   $192.06   $192.05   $192.10  
  Purchase #6 $244.45   8.552%   $265.3554   $265.36   $265.35   $265.40  
  Purchase #7 $68.91   9.628%   $75.5447   $75.54   $75.55   $75.50  
  7 purchase totals = $1,060.82       $1,159.1380   $1,159.13   $1,159.10   $1,159.30