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	$124.55	4.619%	$130.303	$130.30	$130.30	$130.30
Purchase #2	$191.72	6.834%	$204.8221	$204.82	$204.80	$204.80
Purchase #3	$87.62	13.311%	$99.2831	$99.28	$99.30	$99.30
Purchase #4	$120.35	6.118%	$127.713	$127.71	$127.70	$127.70
Purchase #5	$137.84	11.286%	$153.3966	$153.40	$153.40	$153.40
Purchase #6	$41.30	10.246%	$45.5316	$45.53	$45.55	$45.50
Purchase #7	$220.95	11.767%	$246.9492	$246.95	$246.95	$246.90
7 purchase totals =	$924.33		$1,007.9986	$1,007.99	$1,008.00	$1,007.90