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 $148.33   8.775%   $161.346   $161.35   $161.35   $161.30  
  Purchase #2 $191.84   3.558%   $198.6657   $198.67   $198.65   $198.70  
  Purchase #3 $52.67   11.268%   $58.6049   $58.60   $58.60   $58.60  
  Purchase #4 $116.25   12.205%   $130.4383   $130.44   $130.45   $130.40  
  Purchase #5 $229.75   6.621%   $244.9617   $244.96   $244.95   $245.00  
  Purchase #6 $129.57   11.324%   $144.2425   $144.24   $144.25   $144.20  
  Purchase #7 $87.63   9.749%   $96.173   $96.17   $96.15   $96.20  
  7 purchase totals = $956.04       $1,034.4321   $1,034.43   $1,034.40   $1,034.40