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 $144.56   4.437%   $150.9741   $150.97   $150.95   $151.00  
  Purchase #2 $185.73   4.347%   $193.8037   $193.80   $193.80   $193.80  
  Purchase #3 $248.88   10.134%   $274.1015   $274.10   $274.10   $274.10  
  Purchase #4 $199.37   13.377%   $226.0397   $226.04   $226.05   $226.00  
  Purchase #5 $69.96   9.119%   $76.3397   $76.34   $76.35   $76.30  
  Purchase #6 $125.69   4.539%   $131.3951   $131.40   $131.40   $131.40  
  Purchase #7 $53.59   8.566%   $58.1805   $58.18   $58.20   $58.20  
  7 purchase totals = $1,027.78       $1,110.8343   $1,110.83   $1,110.85   $1,110.80