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 $246.41   8.428%   $267.1774   $267.18   $267.20   $267.20  
  Purchase #2 $105.44   4.131%   $109.7957   $109.80   $109.80   $109.80  
  Purchase #3 $188.46   7.137%   $201.9104   $201.91   $201.90   $201.90  
  Purchase #4 $133.69   13.538%   $151.789   $151.79   $151.80   $151.80  
  Purchase #5 $110.36   5.102%   $115.9906   $115.99   $116.00   $116.00  
  Purchase #6 $68.74   3.282%   $70.996   $71.00   $71.00   $71.00  
  Purchase #7 $115.87   6.574%   $123.4873   $123.49   $123.50   $123.50  
  7 purchase totals = $968.97       $1,041.1464   $1,041.16   $1,041.20   $1,041.20