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 $65.45   5.191%   $68.8475   $68.85   $68.85   $68.80  
  Purchase #2 $187.54   7.791%   $202.1512   $202.15   $202.15   $202.20  
  Purchase #3 $87.77   5.871%   $92.923   $92.92   $92.90   $92.90  
  Purchase #4 $84.48   12.274%   $94.8491   $94.85   $94.85   $94.80  
  Purchase #5 $8.59   11.479%   $9.576   $9.58   $9.60   $9.60  
  Purchase #6 $193.88   5.562%   $204.6636   $204.66   $204.65   $204.70  
  Purchase #7 $60.30   7.612%   $64.89   $64.89   $64.90   $64.90  
  7 purchase totals = $688.01       $737.9004   $737.90   $737.90   $737.90