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 $185.58   4.820%   $194.525   $194.53   $194.55   $194.50  
  Purchase #2 $101.95   8.364%   $110.4771   $110.48   $110.50   $110.50  
  Purchase #3 $148.91   10.139%   $164.008   $164.01   $164.00   $164.00  
  Purchase #4 $247.40   11.335%   $275.4428   $275.44   $275.45   $275.40  
  Purchase #5 $195.44   4.362%   $203.9651   $203.97   $203.95   $204.00  
  Purchase #6 $228.39   8.745%   $248.3627   $248.36   $248.35   $248.40  
  Purchase #7 $62.79   3.845%   $65.2043   $65.20   $65.20   $65.20  
  7 purchase totals = $1,170.46       $1,261.9850   $1,261.99   $1,262.00   $1,262.00