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 $214.95   10.511%   $237.5434   $237.54   $237.55   $237.50  
  Purchase #2 $124.96   6.141%   $132.6338   $132.63   $132.65   $132.60  
  Purchase #3 $200.69   4.657%   $210.0361   $210.04   $210.05   $210.00  
  Purchase #4 $69.93   8.702%   $76.0153   $76.02   $76.00   $76.00  
  Purchase #5 $244.81   10.526%   $270.5787   $270.58   $270.60   $270.60  
  Purchase #6 $56.83   4.726%   $59.5158   $59.52   $59.50   $59.50  
  Purchase #7 $134.33   7.332%   $144.1791   $144.18   $144.20   $144.20  
  7 purchase totals = $1,046.50       $1,130.5022   $1,130.51   $1,130.55   $1,130.40