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 $102.76   11.217%   $114.2866   $114.29   $114.30   $114.30  
  Purchase #2 $97.52   5.269%   $102.6583   $102.66   $102.65   $102.70  
  Purchase #3 $217.70   7.446%   $233.9099   $233.91   $233.90   $233.90  
  Purchase #4 $40.42   7.832%   $43.5857   $43.59   $43.60   $43.60  
  Purchase #5 $125.89   7.552%   $135.3972   $135.40   $135.40   $135.40  
  Purchase #6 $94.55   10.620%   $104.5912   $104.59   $104.60   $104.60  
  Purchase #7 $210.65   7.758%   $226.9922   $226.99   $227.00   $227.00  
  7 purchase totals = $889.49       $961.4211   $961.43   $961.45   $961.50