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 $110.63   7.832%   $119.2945   $119.29   $119.30   $119.30  
  Purchase #2 $127.29   10.255%   $140.3436   $140.34   $140.35   $140.30  
  Purchase #3 $153.73   10.519%   $169.9009   $169.90   $169.90   $169.90  
  Purchase #4 $62.94   3.296%   $65.0145   $65.01   $65.00   $65.00  
  Purchase #5 $205.67   9.775%   $225.7742   $225.77   $225.75   $225.80  
  Purchase #6 $201.55   5.442%   $212.5184   $212.52   $212.50   $212.50  
  Purchase #7 $233.57   12.431%   $262.6051   $262.61   $262.60   $262.60  
  7 purchase totals = $1,095.38       $1,195.4512   $1,195.44   $1,195.40   $1,195.40