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 $81.63   5.331%   $85.9817   $85.98   $86.00   $86.00  
  Purchase #2 $234.35   9.153%   $255.8001   $255.80   $255.80   $255.80  
  Purchase #3 $49.91   10.488%   $55.1446   $55.14   $55.15   $55.10  
  Purchase #4 $73.34   3.262%   $75.7324   $75.73   $75.75   $75.70  
  Purchase #5 $210.86   12.193%   $236.5702   $236.57   $236.55   $236.60  
  Purchase #6 $112.64   12.144%   $126.319   $126.32   $126.30   $126.30  
  Purchase #7 $178.59   9.205%   $195.0292   $195.03   $195.05   $195.00  
  7 purchase totals = $941.32       $1,030.5772   $1,030.57   $1,030.60   $1,030.50