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 $88.71   6.566%   $94.5347   $94.53   $94.55   $94.50  
  Purchase #2 $115.95   10.615%   $128.2581   $128.26   $128.25   $128.30  
  Purchase #3 $117.80   3.683%   $122.1386   $122.14   $122.15   $122.10  
  Purchase #4 $141.67   8.510%   $153.7261   $153.73   $153.75   $153.70  
  Purchase #5 $180.41   13.614%   $204.971   $204.97   $204.95   $205.00  
  Purchase #6 $81.75   4.146%   $85.1394   $85.14   $85.15   $85.10  
  Purchase #7 $216.25   6.806%   $230.968   $230.97   $230.95   $231.00  
  7 purchase totals = $942.54       $1,019.7359   $1,019.74   $1,019.75   $1,019.70