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 $195.71   5.435%   $206.3468   $206.35   $206.35   $206.30  
  Purchase #2 $230.98   12.238%   $259.2473   $259.25   $259.25   $259.20  
  Purchase #3 $232.36   12.164%   $260.6243   $260.62   $260.60   $260.60  
  Purchase #4 $162.28   13.251%   $183.7837   $183.78   $183.80   $183.80  
  Purchase #5 $155.98   4.523%   $163.035   $163.04   $163.05   $163.00  
  Purchase #6 $170.35   8.299%   $184.4873   $184.49   $184.50   $184.50  
  Purchase #7 $218.47   9.208%   $238.5867   $238.59   $238.60   $238.60  
  7 purchase totals = $1,366.13       $1,496.1111   $1,496.12   $1,496.15   $1,496.00