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	$225.91	4.288%	$235.597	$235.60	$235.60	$235.60
Purchase #2	$70.88	6.464%	$75.4617	$75.46	$75.45	$75.50
Purchase #3	$247.77	3.346%	$256.0604	$256.06	$256.05	$256.10
Purchase #4	$30.78	6.633%	$32.8216	$32.82	$32.80	$32.80
Purchase #5	$173.26	4.182%	$180.5057	$180.51	$180.50	$180.50
Purchase #6	$182.84	7.315%	$196.2147	$196.21	$196.20	$196.20
Purchase #7	$166.31	9.324%	$181.8167	$181.82	$181.80	$181.80
7 purchase totals =	$1,097.75		$1,158.4778	$1,158.48	$1,158.40	$1,158.50