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 $195.74   7.625%   $210.6652   $210.67   $210.65   $210.70  
  Purchase #2 $144.79   6.787%   $154.6169   $154.62   $154.60   $154.60  
  Purchase #3 $208.85   12.412%   $234.7725   $234.77   $234.75   $234.80  
  Purchase #4 $80.62   5.664%   $85.1863   $85.19   $85.20   $85.20  
  Purchase #5 $62.26   5.415%   $65.6314   $65.63   $65.65   $65.60  
  Purchase #6 $35.27   6.802%   $37.6691   $37.67   $37.65   $37.70  
  Purchase #7 $217.41   8.497%   $235.8833   $235.88   $235.90   $235.90  
  7 purchase totals = $944.94       $1,024.4247   $1,024.43   $1,024.40   $1,024.50