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 $156.45   3.536%   $161.9821   $161.98   $162.00   $162.00  
  Purchase #2 $145.89   9.483%   $159.7247   $159.72   $159.70   $159.70  
  Purchase #3 $100.47   5.123%   $105.6171   $105.62   $105.60   $105.60  
  Purchase #4 $134.53   9.169%   $146.8651   $146.87   $146.85   $146.90  
  Purchase #5 $206.59   8.528%   $224.208   $224.21   $224.20   $224.20  
  Purchase #6 $85.25   9.117%   $93.0222   $93.02   $93.00   $93.00  
  Purchase #7 $49.71   7.248%   $53.313   $53.31   $53.30   $53.30  
  7 purchase totals = $878.89       $944.7322   $944.73   $944.65   $944.70