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 $84.47   13.608%   $95.9647   $95.96   $95.95   $96.00  
  Purchase #2 $148.60   3.136%   $153.2601   $153.26   $153.25   $153.30  
  Purchase #3 $178.50   13.735%   $203.017   $203.02   $203.00   $203.00  
  Purchase #4 $54.88   3.441%   $56.7684   $56.77   $56.75   $56.80  
  Purchase #5 $95.26   8.817%   $103.6591   $103.66   $103.65   $103.70  
  Purchase #6 $52.47   3.577%   $54.3469   $54.35   $54.35   $54.30  
  Purchase #7 $220.43   12.114%   $247.1329   $247.13   $247.15   $247.10  
  7 purchase totals = $834.61       $914.1491   $914.15   $914.10   $914.20