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 $46.65   5.674%   $49.2969   $49.30   $49.30   $49.30  
  Purchase #2 $205.61   10.753%   $227.7192   $227.72   $227.70   $227.70  
  Purchase #3 $64.85   5.106%   $68.1612   $68.16   $68.15   $68.20  
  Purchase #4 $116.73   6.598%   $124.4318   $124.43   $124.45   $124.40  
  Purchase #5 $185.42   5.149%   $194.9673   $194.97   $194.95   $195.00  
  Purchase #6 $226.39   12.546%   $254.7929   $254.79   $254.80   $254.80  
  Purchase #7 $189.72   5.246%   $199.6727   $199.67   $199.65   $199.70  
  7 purchase totals = $1,035.37       $1,119.0420   $1,119.04   $1,119.00   $1,119.10