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 $176.76   10.692%   $195.6592   $195.66   $195.65   $195.70  
  Purchase #2 $54.41   12.782%   $61.3647   $61.36   $61.35   $61.40  
  Purchase #3 $153.80   3.150%   $158.6447   $158.64   $158.65   $158.60  
  Purchase #4 $77.92   10.158%   $85.8351   $85.84   $85.85   $85.80  
  Purchase #5 $60.96   5.313%   $64.1988   $64.20   $64.20   $64.20  
  Purchase #6 $18.97   10.396%   $20.9421   $20.94   $20.95   $20.90  
  Purchase #7 $67.73   9.666%   $74.2768   $74.28   $74.30   $74.30  
  7 purchase totals = $610.55       $660.9214   $660.92   $660.95   $660.90