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 $53.92   6.819%   $57.5968   $57.60   $57.60   $57.60  
  Purchase #2 $182.44   8.402%   $197.7686   $197.77   $197.75   $197.80  
  Purchase #3 $216.46   11.275%   $240.8659   $240.87   $240.85   $240.90  
  Purchase #4 $119.99   10.207%   $132.2374   $132.24   $132.25   $132.20  
  Purchase #5 $225.78   8.333%   $244.5942   $244.59   $244.60   $244.60  
  Purchase #6 $119.70   7.341%   $128.4872   $128.49   $128.50   $128.50  
  Purchase #7 $173.81   11.822%   $194.3578   $194.36   $194.35   $194.40  
  7 purchase totals = $1,092.10       $1,195.9079   $1,195.92   $1,195.90   $1,196.00