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 $233.43   12.580%   $262.7955   $262.80   $262.80   $262.80  
  Purchase #2 $166.40   10.831%   $184.4228   $184.42   $184.40   $184.40  
  Purchase #3 $97.96   6.150%   $103.9845   $103.98   $104.00   $104.00  
  Purchase #4 $220.26   11.211%   $244.9533   $244.95   $244.95   $245.00  
  Purchase #5 $226.71   5.440%   $239.043   $239.04   $239.05   $239.00  
  Purchase #6 $223.41   8.471%   $242.3351   $242.34   $242.35   $242.30  
  Purchase #7 $167.76   9.557%   $183.7928   $183.79   $183.80   $183.80  
  7 purchase totals = $1,335.93       $1,461.3270   $1,461.32   $1,461.35   $1,461.30