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 $62.40   7.283%   $66.9446   $66.94   $66.95   $66.90  
  Purchase #2 $128.73   5.864%   $136.2787   $136.28   $136.30   $136.30  
  Purchase #3 $44.46   8.422%   $48.2044   $48.20   $48.20   $48.20  
  Purchase #4 $242.91   5.776%   $256.9405   $256.94   $256.95   $256.90  
  Purchase #5 $156.88   6.681%   $167.3612   $167.36   $167.35   $167.40  
  Purchase #6 $202.66   9.126%   $221.1548   $221.15   $221.15   $221.20  
  Purchase #7 $188.74   6.414%   $200.8458   $200.85   $200.85   $200.80  
  7 purchase totals = $1,026.78       $1,097.7300   $1,097.72   $1,097.75   $1,097.70