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 $176.78   10.826%   $195.9182   $195.92   $195.90   $195.90  
  Purchase #2 $190.66   4.662%   $199.5486   $199.55   $199.55   $199.50  
  Purchase #3 $67.83   5.386%   $71.4833   $71.48   $71.50   $71.50  
  Purchase #4 $73.53   3.143%   $75.841   $75.84   $75.85   $75.80  
  Purchase #5 $232.46   4.604%   $243.1625   $243.16   $243.15   $243.20  
  Purchase #6 $116.68   7.812%   $125.795   $125.80   $125.80   $125.80  
  Purchase #7 $212.47   11.507%   $236.9189   $236.92   $236.90   $236.90  
  7 purchase totals = $1,070.41       $1,148.6675   $1,148.67   $1,148.65   $1,148.60