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 $67.38   7.827%   $72.6538   $72.65   $72.65   $72.70  
  Purchase #2 $184.52   11.519%   $205.7749   $205.77   $205.75   $205.80  
  Purchase #3 $37.63   9.563%   $41.2286   $41.23   $41.25   $41.20  
  Purchase #4 $24.67   9.211%   $26.9424   $26.94   $26.95   $26.90  
  Purchase #5 $124.99   9.710%   $137.1265   $137.13   $137.15   $137.10  
  Purchase #6 $154.43   4.581%   $161.5044   $161.50   $161.50   $161.50  
  Purchase #7 $161.32   11.125%   $179.2669   $179.27   $179.25   $179.30  
  7 purchase totals = $754.94       $824.4975   $824.49   $824.50   $824.50