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 $59.86   13.844%   $68.147   $68.15   $68.15   $68.10  
  Purchase #2 $175.63   8.672%   $190.8606   $190.86   $190.85   $190.90  
  Purchase #3 $88.68   5.567%   $93.6168   $93.62   $93.60   $93.60  
  Purchase #4 $139.85   3.463%   $144.693   $144.69   $144.70   $144.70  
  Purchase #5 $125.94   9.806%   $138.2897   $138.29   $138.30   $138.30  
  Purchase #6 $240.44   5.584%   $253.8662   $253.87   $253.85   $253.90  
  Purchase #7 $166.39   4.144%   $173.2852   $173.29   $173.30   $173.30  
  7 purchase totals = $996.79       $1,062.7585   $1,062.77   $1,062.75   $1,062.80