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 $65.43   8.438%   $70.951   $70.95   $70.95   $71.00  
  Purchase #2 $239.36   9.817%   $262.858   $262.86   $262.85   $262.90  
  Purchase #3 $159.62   9.234%   $174.3593   $174.36   $174.35   $174.40  
  Purchase #4 $19.95   11.767%   $22.2975   $22.30   $22.30   $22.30  
  Purchase #5 $240.36   11.133%   $267.1193   $267.12   $267.10   $267.10  
  Purchase #6 $90.27   4.647%   $94.4648   $94.46   $94.45   $94.50  
  Purchase #7 $237.27   10.570%   $262.3494   $262.35   $262.35   $262.30  
  7 purchase totals = $1,052.26       $1,154.3993   $1,154.40   $1,154.35   $1,154.50