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 $62.75   10.790%   $69.5207   $69.52   $69.50   $69.50  
  Purchase #2 $75.44   10.562%   $83.408   $83.41   $83.40   $83.40  
  Purchase #3 $114.38   4.313%   $119.3132   $119.31   $119.30   $119.30  
  Purchase #4 $17.51   10.801%   $19.4013   $19.40   $19.40   $19.40  
  Purchase #5 $192.52   5.775%   $203.638   $203.64   $203.65   $203.60  
  Purchase #6 $72.59   3.385%   $75.0472   $75.05   $75.05   $75.00  
  Purchase #7 $159.48   5.571%   $168.3646   $168.36   $168.35   $168.40  
  7 purchase totals = $694.67       $738.6930   $738.69   $738.65   $738.60