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 $204.80   11.353%   $228.0509   $228.05   $228.05   $228.10  
  Purchase #2 $62.99   13.133%   $71.2625   $71.26   $71.25   $71.30  
  Purchase #3 $179.53   5.846%   $190.0253   $190.03   $190.05   $190.00  
  Purchase #4 $190.91   4.624%   $199.7377   $199.74   $199.75   $199.70  
  Purchase #5 $195.33   11.356%   $217.5117   $217.51   $217.50   $217.50  
  Purchase #6 $189.84   6.146%   $201.5076   $201.51   $201.50   $201.50  
  Purchase #7 $55.33   9.223%   $60.4331   $60.43   $60.45   $60.40  
  7 purchase totals = $1,078.73       $1,168.5288   $1,168.53   $1,168.55   $1,168.50