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 $21.94   3.742%   $22.761   $22.76   $22.75   $22.80  
  Purchase #2 $62.44   3.372%   $64.5455   $64.55   $64.55   $64.50  
  Purchase #3 $214.53   6.164%   $227.7536   $227.75   $227.75   $227.80  
  Purchase #4 $25.39   6.444%   $27.0261   $27.03   $27.05   $27.00  
  Purchase #5 $192.29   11.463%   $214.3322   $214.33   $214.35   $214.30  
  Purchase #6 $140.81   3.244%   $145.3779   $145.38   $145.40   $145.40  
  Purchase #7 $55.25   7.153%   $59.202   $59.20   $59.20   $59.20  
  7 purchase totals = $712.65       $760.9983   $761.00   $761.05   $761.00