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 $192.86   11.171%   $214.4044   $214.40   $214.40   $214.40  
  Purchase #2 $189.42   8.192%   $204.9373   $204.94   $204.95   $204.90  
  Purchase #3 $9.45   13.698%   $10.7445   $10.74   $10.75   $10.70  
  Purchase #4 $55.49   12.485%   $62.4179   $62.42   $62.40   $62.40  
  Purchase #5 $124.87   13.380%   $141.5776   $141.58   $141.60   $141.60  
  Purchase #6 $13.84   3.629%   $14.3423   $14.34   $14.35   $14.30  
  Purchase #7 $105.43   13.543%   $119.7084   $119.71   $119.70   $119.70  
  7 purchase totals = $691.36       $768.1324   $768.13   $768.15   $768.00