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 $218.53   7.381%   $234.6597   $234.66   $234.65   $234.70  
  Purchase #2 $48.58   9.506%   $53.198   $53.20   $53.20   $53.20  
  Purchase #3 $33.52   3.126%   $34.5678   $34.57   $34.55   $34.60  
  Purchase #4 $114.82   9.642%   $125.8909   $125.89   $125.90   $125.90  
  Purchase #5 $167.90   3.388%   $173.5885   $173.59   $173.60   $173.60  
  Purchase #6 $175.66   13.665%   $199.6639   $199.66   $199.65   $199.70  
  Purchase #7 $85.93   8.142%   $92.9264   $92.93   $92.95   $92.90  
  7 purchase totals = $844.94       $914.4952   $914.50   $914.50   $914.60