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 $166.27   11.241%   $184.9604   $184.96   $184.95   $185.00  
  Purchase #2 $224.42   7.118%   $240.3942   $240.39   $240.40   $240.40  
  Purchase #3 $212.29   7.119%   $227.4029   $227.40   $227.40   $227.40  
  Purchase #4 $116.43   7.575%   $125.2496   $125.25   $125.25   $125.20  
  Purchase #5 $14.79   7.507%   $15.9003   $15.90   $15.90   $15.90  
  Purchase #6 $175.96   9.788%   $193.183   $193.18   $193.20   $193.20  
  Purchase #7 $97.91   11.847%   $109.5094   $109.51   $109.50   $109.50  
  7 purchase totals = $1,008.07       $1,096.5998   $1,096.59   $1,096.60   $1,096.60