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 $208.98   8.252%   $226.225   $226.23   $226.25   $226.20  
  Purchase #2 $169.30   7.814%   $182.5291   $182.53   $182.55   $182.50  
  Purchase #3 $181.36   7.486%   $194.9366   $194.94   $194.95   $194.90  
  Purchase #4 $234.26   6.718%   $249.9976   $250.00   $250.00   $250.00  
  Purchase #5 $65.56   10.278%   $72.2983   $72.30   $72.30   $72.30  
  Purchase #6 $63.54   7.531%   $68.3252   $68.33   $68.35   $68.30  
  Purchase #7 $103.52   3.299%   $106.9351   $106.94   $106.95   $106.90  
  7 purchase totals = $1,026.52       $1,101.2469   $1,101.27   $1,101.35   $1,101.10