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 $61.26   13.447%   $69.4976   $69.50   $69.50   $69.50  
  Purchase #2 $202.33   7.414%   $217.3307   $217.33   $217.35   $217.30  
  Purchase #3 $202.62   11.367%   $225.6518   $225.65   $225.65   $225.70  
  Purchase #4 $31.77   13.578%   $36.0837   $36.08   $36.10   $36.10  
  Purchase #5 $158.53   6.233%   $168.4112   $168.41   $168.40   $168.40  
  Purchase #6 $87.72   11.664%   $97.9517   $97.95   $97.95   $98.00  
  Purchase #7 $103.83   11.192%   $115.4507   $115.45   $115.45   $115.50  
  7 purchase totals = $848.06       $930.3774   $930.37   $930.40   $930.50