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	$127.98	5.354%	$134.832	$134.83	$134.85	$134.80
Purchase #2	$42.51	5.859%	$45.0007	$45.00	$45.00	$45.00
Purchase #3	$162.35	8.229%	$175.7098	$175.71	$175.70	$175.70
Purchase #4	$166.41	13.113%	$188.2313	$188.23	$188.25	$188.20
Purchase #5	$30.45	12.536%	$34.2672	$34.27	$34.25	$34.30
Purchase #6	$229.95	10.501%	$254.097	$254.10	$254.10	$254.10
Purchase #7	$216.51	7.809%	$233.4173	$233.42	$233.40	$233.40
7 purchase totals =	$976.16		$1,065.5553	$1,065.56	$1,065.55	$1,065.50