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 $69.33   10.154%   $76.3698   $76.37   $76.35   $76.40  
  Purchase #2 $245.92   5.133%   $258.5431   $258.54   $258.55   $258.50  
  Purchase #3 $65.74   5.732%   $69.5082   $69.51   $69.50   $69.50  
  Purchase #4 $224.49   9.863%   $246.6314   $246.63   $246.65   $246.60  
  Purchase #5 $213.98   10.415%   $236.266   $236.27   $236.25   $236.30  
  Purchase #6 $71.83   5.828%   $76.0163   $76.02   $76.00   $76.00  
  Purchase #7 $44.77   9.481%   $49.0146   $49.01   $49.00   $49.00  
  7 purchase totals = $936.06       $1,012.3494   $1,012.35   $1,012.30   $1,012.30