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 $75.70   8.654%   $82.2511   $82.25   $82.25   $82.30  
  Purchase #2 $213.88   5.584%   $225.8231   $225.82   $225.80   $225.80  
  Purchase #3 $86.53   9.232%   $94.5184   $94.52   $94.50   $94.50  
  Purchase #4 $162.62   8.343%   $176.1874   $176.19   $176.20   $176.20  
  Purchase #5 $149.99   12.755%   $169.1212   $169.12   $169.10   $169.10  
  Purchase #6 $41.90   3.854%   $43.5148   $43.51   $43.50   $43.50  
  Purchase #7 $224.56   4.117%   $233.8051   $233.81   $233.80   $233.80  
  7 purchase totals = $955.18       $1,025.2211   $1,025.22   $1,025.15   $1,025.20