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	$227.95	3.211%	$235.2695	$235.27	$235.25	$235.30
Purchase #2	$41.65	9.486%	$45.6009	$45.60	$45.60	$45.60
Purchase #3	$111.41	11.304%	$124.0038	$124.00	$124.00	$124.00
Purchase #4	$166.57	13.780%	$189.5233	$189.52	$189.50	$189.50
Purchase #5	$165.70	3.462%	$171.4365	$171.44	$171.45	$171.40
Purchase #6	$47.70	5.873%	$50.5014	$50.50	$50.50	$50.50
Purchase #7	$183.71	8.244%	$198.8551	$198.86	$198.85	$198.90
7 purchase totals =	$944.69		$1,015.1905	$1,015.19	$1,015.15	$1,015.20