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 $108.34   9.619%   $118.7612   $118.76   $118.75   $118.80  
  Purchase #2 $244.33   10.399%   $269.7379   $269.74   $269.75   $269.70  
  Purchase #3 $167.62   4.321%   $174.8629   $174.86   $174.85   $174.90  
  Purchase #4 $91.96   12.806%   $103.7364   $103.74   $103.75   $103.70  
  Purchase #5 $16.51   8.656%   $17.9391   $17.94   $17.95   $17.90  
  Purchase #6 $113.55   4.316%   $118.4508   $118.45   $118.45   $118.50  
  Purchase #7 $195.51   12.139%   $219.243   $219.24   $219.25   $219.20  
  7 purchase totals = $937.82       $1,022.7313   $1,022.73   $1,022.75   $1,022.70