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	$67.65	5.673%	$71.4878	$71.49	$71.50	$71.50
Purchase #2	$58.72	5.658%	$62.0424	$62.04	$62.05	$62.00
Purchase #3	$158.63	9.252%	$173.3064	$173.31	$173.30	$173.30
Purchase #4	$204.41	12.454%	$229.8672	$229.87	$229.85	$229.90
Purchase #5	$146.29	13.121%	$165.4847	$165.48	$165.50	$165.50
Purchase #6	$200.39	11.421%	$223.2765	$223.28	$223.30	$223.30
Purchase #7	$246.32	10.776%	$272.8634	$272.86	$272.85	$272.90
7 purchase totals =	$1,082.41		$1,198.3284	$1,198.33	$1,198.35	$1,198.40