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 $89.32   6.513%   $95.1374   $95.14   $95.15   $95.10  
  Purchase #2 $205.52   4.471%   $214.7088   $214.71   $214.70   $214.70  
  Purchase #3 $228.40   12.166%   $256.1871   $256.19   $256.20   $256.20  
  Purchase #4 $243.73   7.683%   $262.4558   $262.46   $262.45   $262.50  
  Purchase #5 $71.41   6.423%   $75.9967   $76.00   $76.00   $76.00  
  Purchase #6 $45.75   12.119%   $51.2944   $51.29   $51.30   $51.30  
  Purchase #7 $78.70   12.487%   $88.5273   $88.53   $88.55   $88.50  
  7 purchase totals = $962.83       $1,044.3075   $1,044.32   $1,044.35   $1,044.30