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 $171.82   13.863%   $195.6394   $195.64   $195.65   $195.60  
  Purchase #2 $175.35   5.609%   $185.1854   $185.19   $185.20   $185.20  
  Purchase #3 $244.57   9.277%   $267.2588   $267.26   $267.25   $267.30  
  Purchase #4 $222.77   5.770%   $235.6238   $235.62   $235.60   $235.60  
  Purchase #5 $219.67   12.292%   $246.6718   $246.67   $246.65   $246.70  
  Purchase #6 $28.43   13.749%   $32.3388   $32.34   $32.35   $32.30  
  Purchase #7 $150.77   13.739%   $171.4843   $171.48   $171.50   $171.50  
  7 purchase totals = $1,213.38       $1,334.2023   $1,334.20   $1,334.20   $1,334.20