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 $217.29   8.564%   $235.8987   $235.90   $235.90   $235.90  
  Purchase #2 $169.27   11.536%   $188.797   $188.80   $188.80   $188.80  
  Purchase #3 $192.61   8.539%   $209.057   $209.06   $209.05   $209.10  
  Purchase #4 $178.53   8.219%   $193.2034   $193.20   $193.20   $193.20  
  Purchase #5 $201.92   6.219%   $214.4774   $214.48   $214.50   $214.50  
  Purchase #6 $107.91   7.563%   $116.0712   $116.07   $116.05   $116.10  
  Purchase #7 $115.73   3.216%   $119.4519   $119.45   $119.45   $119.50  
  7 purchase totals = $1,183.26       $1,276.9566   $1,276.96   $1,276.95   $1,277.10