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 $68.95   5.300%   $72.6044   $72.60   $72.60   $72.60  
  Purchase #2 $210.38   10.469%   $232.4047   $232.40   $232.40   $232.40  
  Purchase #3 $50.58   4.198%   $52.7033   $52.70   $52.70   $52.70  
  Purchase #4 $119.31   10.304%   $131.6037   $131.60   $131.60   $131.60  
  Purchase #5 $182.93   11.359%   $203.709   $203.71   $203.70   $203.70  
  Purchase #6 $133.57   8.450%   $144.8567   $144.86   $144.85   $144.90  
  Purchase #7 $43.40   8.783%   $47.2118   $47.21   $47.20   $47.20  
  7 purchase totals = $809.12       $885.0936   $885.08   $885.05   $885.10