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 $221.95   10.200%   $244.5889   $244.59   $244.60   $244.60  
  Purchase #2 $206.55   6.435%   $219.8415   $219.84   $219.85   $219.80  
  Purchase #3 $32.63   11.155%   $36.2699   $36.27   $36.25   $36.30  
  Purchase #4 $235.86   6.420%   $251.0022   $251.00   $251.00   $251.00  
  Purchase #5 $248.35   4.708%   $260.0423   $260.04   $260.05   $260.00  
  Purchase #6 $212.25   7.291%   $227.7251   $227.73   $227.75   $227.70  
  Purchase #7 $240.53   4.325%   $250.9329   $250.93   $250.95   $250.90  
  7 purchase totals = $1,398.12       $1,490.4028   $1,490.40   $1,490.45   $1,490.30