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 $113.29   11.445%   $126.256   $126.26   $126.25   $126.30  
  Purchase #2 $31.98   13.789%   $36.3897   $36.39   $36.40   $36.40  
  Purchase #3 $102.49   12.168%   $114.961   $114.96   $114.95   $115.00  
  Purchase #4 $161.26   8.702%   $175.2928   $175.29   $175.30   $175.30  
  Purchase #5 $183.99   5.437%   $193.9935   $193.99   $194.00   $194.00  
  Purchase #6 $117.82   7.322%   $126.4468   $126.45   $126.45   $126.40  
  Purchase #7 $132.44   13.453%   $150.2572   $150.26   $150.25   $150.30  
  7 purchase totals = $843.27       $923.5970   $923.60   $923.60   $923.70