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 $191.36   9.530%   $209.5966   $209.60   $209.60   $209.60  
  Purchase #2 $32.53   8.692%   $35.3575   $35.36   $35.35   $35.40  
  Purchase #3 $169.28   4.563%   $177.0042   $177.00   $177.00   $177.00  
  Purchase #4 $104.88   13.324%   $118.8542   $118.85   $118.85   $118.90  
  Purchase #5 $233.88   4.816%   $245.1437   $245.14   $245.15   $245.10  
  Purchase #6 $169.40   5.235%   $178.2681   $178.27   $178.25   $178.30  
  Purchase #7 $214.29   8.299%   $232.0739   $232.07   $232.05   $232.10  
  7 purchase totals = $1,115.62       $1,196.2982   $1,196.29   $1,196.25   $1,196.40