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 $62.94   9.859%   $69.1453   $69.15   $69.15   $69.10  
  Purchase #2 $191.82   13.133%   $217.0117   $217.01   $217.00   $217.00  
  Purchase #3 $190.29   10.192%   $209.6844   $209.68   $209.70   $209.70  
  Purchase #4 $197.83   3.163%   $204.0874   $204.09   $204.10   $204.10  
  Purchase #5 $187.73   6.310%   $199.5758   $199.58   $199.60   $199.60  
  Purchase #6 $82.56   6.579%   $87.9916   $87.99   $88.00   $88.00  
  Purchase #7 $98.65   7.650%   $106.1967   $106.20   $106.20   $106.20  
  7 purchase totals = $1,011.82       $1,093.6929   $1,093.70   $1,093.75   $1,093.70