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 $88.92   7.321%   $95.4298   $95.43   $95.45   $95.40  
  Purchase #2 $161.59   7.849%   $174.2732   $174.27   $174.25   $174.30  
  Purchase #3 $53.76   8.316%   $58.2307   $58.23   $58.25   $58.20  
  Purchase #4 $224.76   4.601%   $235.1012   $235.10   $235.10   $235.10  
  Purchase #5 $80.95   3.114%   $83.4708   $83.47   $83.45   $83.50  
  Purchase #6 $200.26   3.288%   $206.8445   $206.84   $206.85   $206.80  
  Purchase #7 $14.79   8.790%   $16.09   $16.09   $16.10   $16.10  
  7 purchase totals = $825.03       $869.4402   $869.43   $869.45   $869.40