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	$166.63	4.621%	$174.33	$174.33	$174.35	$174.30
Purchase #2	$159.85	10.433%	$176.5272	$176.53	$176.55	$176.50
Purchase #3	$45.77	9.535%	$50.1342	$50.13	$50.15	$50.10
Purchase #4	$157.37	11.570%	$175.5777	$175.58	$175.60	$175.60
Purchase #5	$147.50	6.126%	$156.5359	$156.54	$156.55	$156.50
Purchase #6	$70.71	7.756%	$76.1943	$76.19	$76.20	$76.20
Purchase #7	$225.45	13.535%	$255.9647	$255.96	$255.95	$256.00
7 purchase totals =	$973.28		$1,065.2640	$1,065.26	$1,065.35	$1,065.20