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 $64.75   5.124%   $68.0678   $68.07   $68.05   $68.10  
  Purchase #2 $186.56   4.102%   $194.2127   $194.21   $194.20   $194.20  
  Purchase #3 $93.40   4.349%   $97.462   $97.46   $97.45   $97.50  
  Purchase #4 $137.56   9.403%   $150.4948   $150.49   $150.50   $150.50  
  Purchase #5 $194.82   11.801%   $217.8107   $217.81   $217.80   $217.80  
  Purchase #6 $246.63   8.789%   $268.3063   $268.31   $268.30   $268.30  
  Purchase #7 $201.98   5.402%   $212.891   $212.89   $212.90   $212.90  
  7 purchase totals = $1,125.70       $1,209.2453   $1,209.24   $1,209.20   $1,209.30