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	$22.79	11.697%	$25.4557	$25.46	$25.45	$25.50
Purchase #2	$186.93	4.596%	$195.5213	$195.52	$195.50	$195.50
Purchase #3	$12.67	12.817%	$14.2939	$14.29	$14.30	$14.30
Purchase #4	$166.66	3.461%	$172.4281	$172.43	$172.45	$172.40
Purchase #5	$89.76	7.752%	$96.7182	$96.72	$96.70	$96.70
Purchase #6	$87.43	3.248%	$90.2697	$90.27	$90.25	$90.30
Purchase #7	$237.41	4.856%	$248.9386	$248.94	$248.95	$248.90
7 purchase totals =	$803.65		$843.6255	$843.63	$843.60	$843.60