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	$239.39	10.429%	$264.356	$264.36	$264.35	$264.40
Purchase #2	$146.63	8.764%	$159.4807	$159.48	$159.50	$159.50
Purchase #3	$149.58	3.721%	$155.1459	$155.15	$155.15	$155.10
Purchase #4	$178.38	4.672%	$186.7139	$186.71	$186.70	$186.70
Purchase #5	$33.68	11.206%	$37.4542	$37.45	$37.45	$37.50
Purchase #6	$210.41	3.156%	$217.0505	$217.05	$217.05	$217.10
Purchase #7	$50.35	8.354%	$54.5562	$54.56	$54.55	$54.60
7 purchase totals =	$1,008.42		$1,074.7574	$1,074.76	$1,074.75	$1,074.90