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 $145.50   4.216%   $151.6343   $151.63   $151.65   $151.60  
  Purchase #2 $185.39   13.572%   $210.5511   $210.55   $210.55   $210.60  
  Purchase #3 $104.95   11.272%   $116.78   $116.78   $116.80   $116.80  
  Purchase #4 $231.71   9.727%   $254.2484   $254.25   $254.25   $254.20  
  Purchase #5 $94.76   11.756%   $105.9   $105.90   $105.90   $105.90  
  Purchase #6 $68.32   9.756%   $74.9853   $74.99   $75.00   $75.00  
  Purchase #7 $233.85   8.277%   $253.2058   $253.21   $253.20   $253.20  
  7 purchase totals = $1,064.48       $1,167.3049   $1,167.31   $1,167.35   $1,167.30