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	$71.77	3.458%	$74.2518	$74.25	$74.25	$74.30
Purchase #2	$50.82	7.407%	$54.5842	$54.58	$54.60	$54.60
Purchase #3	$249.55	6.280%	$265.2217	$265.22	$265.20	$265.20
Purchase #4	$169.61	13.723%	$192.8856	$192.89	$192.90	$192.90
Purchase #5	$6.31	13.465%	$7.1596	$7.16	$7.15	$7.20
Purchase #6	$238.53	10.178%	$262.8076	$262.81	$262.80	$262.80
Purchase #7	$146.99	12.815%	$165.8268	$165.83	$165.85	$165.80
7 purchase totals =	$933.58		$1,022.7373	$1,022.74	$1,022.75	$1,022.80