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 $54.62   13.575%   $62.0347   $62.03   $62.05   $62.00  
  Purchase #2 $189.27   6.765%   $202.0741   $202.07   $202.05   $202.10  
  Purchase #3 $178.64   9.294%   $195.2428   $195.24   $195.25   $195.20  
  Purchase #4 $182.98   4.614%   $191.4227   $191.42   $191.40   $191.40  
  Purchase #5 $191.50   11.830%   $214.1545   $214.15   $214.15   $214.20  
  Purchase #6 $216.59   10.802%   $239.9861   $239.99   $240.00   $240.00  
  Purchase #7 $153.99   10.524%   $170.1959   $170.20   $170.20   $170.20  
  7 purchase totals = $1,167.59       $1,275.1108   $1,275.10   $1,275.10   $1,275.10