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	$240.89	5.579%	$254.3293	$254.33	$254.35	$254.30
Purchase #2	$16.43	7.641%	$17.6854	$17.69	$17.70	$17.70
Purchase #3	$63.82	11.819%	$71.3629	$71.36	$71.35	$71.40
Purchase #4	$211.93	7.751%	$228.3567	$228.36	$228.35	$228.40
Purchase #5	$50.61	4.865%	$53.0722	$53.07	$53.05	$53.10
Purchase #6	$151.47	13.840%	$172.4334	$172.43	$172.45	$172.40
Purchase #7	$91.64	10.122%	$100.9158	$100.92	$100.90	$100.90
7 purchase totals =	$826.79		$898.1557	$898.16	$898.15	$898.20