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 $214.51   10.496%   $237.025   $237.03   $237.05   $237.00  
  Purchase #2 $209.61   13.566%   $238.0457   $238.05   $238.05   $238.00  
  Purchase #3 $104.39   8.200%   $112.95   $112.95   $112.95   $113.00  
  Purchase #4 $221.76   3.348%   $229.1845   $229.18   $229.20   $229.20  
  Purchase #5 $176.26   3.124%   $181.7664   $181.77   $181.75   $181.80  
  Purchase #6 $194.73   11.729%   $217.5699   $217.57   $217.55   $217.60  
  Purchase #7 $26.40   6.160%   $28.0262   $28.03   $28.05   $28.00  
  7 purchase totals = $1,147.66       $1,244.5677   $1,244.58   $1,244.60   $1,244.60