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 $62.35   4.219%   $64.9805   $64.98   $65.00   $65.00  
  Purchase #2 $170.95   8.597%   $185.6466   $185.65   $185.65   $185.60  
  Purchase #3 $172.41   6.305%   $183.2805   $183.28   $183.30   $183.30  
  Purchase #4 $219.51   3.501%   $227.195   $227.20   $227.20   $227.20  
  Purchase #5 $226.35   12.317%   $254.2295   $254.23   $254.25   $254.20  
  Purchase #6 $217.58   3.328%   $224.8211   $224.82   $224.80   $224.80  
  Purchase #7 $158.31   10.701%   $175.2508   $175.25   $175.25   $175.30  
  7 purchase totals = $1,227.46       $1,315.4040   $1,315.41   $1,315.45   $1,315.40