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 $58.75   4.485%   $61.3849   $61.38   $61.40   $61.40  
  Purchase #2 $182.81   11.747%   $204.2847   $204.28   $204.30   $204.30  
  Purchase #3 $224.69   11.707%   $250.9945   $250.99   $251.00   $251.00  
  Purchase #4 $218.37   9.329%   $238.7417   $238.74   $238.75   $238.70  
  Purchase #5 $49.33   10.590%   $54.554   $54.55   $54.55   $54.60  
  Purchase #6 $174.32   11.588%   $194.5202   $194.52   $194.50   $194.50  
  Purchase #7 $218.96   13.635%   $248.8152   $248.82   $248.80   $248.80  
  7 purchase totals = $1,127.23       $1,253.2952   $1,253.28   $1,253.30   $1,253.30