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	$166.42	4.448%	$173.8224	$173.82	$173.80	$173.80
Purchase #2	$60.71	5.525%	$64.0642	$64.06	$64.05	$64.10
Purchase #3	$129.71	10.463%	$143.2816	$143.28	$143.30	$143.30
Purchase #4	$167.41	12.629%	$188.5522	$188.55	$188.55	$188.60
Purchase #5	$68.26	4.529%	$71.3515	$71.35	$71.35	$71.40
Purchase #6	$247.89	6.456%	$263.8938	$263.89	$263.90	$263.90
Purchase #7	$171.61	3.747%	$178.0402	$178.04	$178.05	$178.00
7 purchase totals =	$1,012.01		$1,083.0059	$1,082.99	$1,083.00	$1,083.10