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 $69.82   10.232%   $76.964   $76.96   $76.95   $77.00  
  Purchase #2 $12.82   6.263%   $13.6229   $13.62   $13.60   $13.60  
  Purchase #3 $194.84   7.442%   $209.34   $209.34   $209.35   $209.30  
  Purchase #4 $61.48   10.337%   $67.8352   $67.84   $67.85   $67.80  
  Purchase #5 $170.70   8.203%   $184.7025   $184.70   $184.70   $184.70  
  Purchase #6 $50.80   3.141%   $52.3956   $52.40   $52.40   $52.40  
  Purchase #7 $122.26   8.399%   $132.5286   $132.53   $132.55   $132.50  
  7 purchase totals = $682.72       $737.3888   $737.39   $737.40   $737.30