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	$142.83	7.417%	$153.4237	$153.42	$153.40	$153.40
Purchase #2	$176.63	10.718%	$195.5612	$195.56	$195.55	$195.60
Purchase #3	$223.83	6.327%	$237.9917	$237.99	$238.00	$238.00
Purchase #4	$20.63	5.209%	$21.7046	$21.70	$21.70	$21.70
Purchase #5	$169.53	6.105%	$179.8798	$179.88	$179.90	$179.90
Purchase #6	$110.53	11.760%	$123.5283	$123.53	$123.55	$123.50
Purchase #7	$96.39	6.771%	$102.9166	$102.92	$102.90	$102.90
7 purchase totals =	$940.37		$1,015.0059	$1,015.00	$1,015.00	$1,015.00