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	$33.83	8.765%	$36.7952	$36.80	$36.80	$36.80
Purchase #2	$118.65	7.287%	$127.296	$127.30	$127.30	$127.30
Purchase #3	$196.36	5.166%	$206.504	$206.50	$206.50	$206.50
Purchase #4	$83.95	7.719%	$90.4301	$90.43	$90.45	$90.40
Purchase #5	$152.26	6.501%	$162.1584	$162.16	$162.15	$162.20
Purchase #6	$207.27	9.125%	$226.1834	$226.18	$226.20	$226.20
Purchase #7	$140.69	12.563%	$158.3649	$158.36	$158.35	$158.40
7 purchase totals =	$933.01		$1,007.7320	$1,007.73	$1,007.75	$1,007.80