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 $72.51   6.134%   $76.9578   $76.96   $76.95   $77.00  
  Purchase #2 $214.84   5.813%   $227.3286   $227.33   $227.35   $227.30  
  Purchase #3 $183.70   10.847%   $203.6259   $203.63   $203.65   $203.60  
  Purchase #4 $236.40   12.697%   $266.4157   $266.42   $266.40   $266.40  
  Purchase #5 $48.44   6.655%   $51.6637   $51.66   $51.65   $51.70  
  Purchase #6 $87.28   11.566%   $97.3748   $97.37   $97.35   $97.40  
  Purchase #7 $31.43   5.288%   $33.092   $33.09   $33.10   $33.10  
  7 purchase totals = $874.60       $956.4585   $956.46   $956.45   $956.50