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 $182.76   7.570%   $196.5949   $196.59   $196.60   $196.60  
  Purchase #2 $196.43   7.214%   $210.6005   $210.60   $210.60   $210.60  
  Purchase #3 $116.35   8.266%   $125.9675   $125.97   $125.95   $126.00  
  Purchase #4 $243.70   11.406%   $271.4964   $271.50   $271.50   $271.50  
  Purchase #5 $169.60   10.846%   $187.9948   $187.99   $188.00   $188.00  
  Purchase #6 $26.76   12.511%   $30.1079   $30.11   $30.10   $30.10  
  Purchase #7 $153.31   8.685%   $166.625   $166.63   $166.65   $166.60  
  7 purchase totals = $1,088.91       $1,189.3870   $1,189.39   $1,189.40   $1,189.40