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	$167.26	3.422%	$172.9836	$172.98	$173.00	$173.00
Purchase #2	$137.69	11.238%	$153.1636	$153.16	$153.15	$153.20
Purchase #3	$36.26	4.552%	$37.9106	$37.91	$37.90	$37.90
Purchase #4	$12.43	13.182%	$14.0685	$14.07	$14.05	$14.10
Purchase #5	$181.26	9.729%	$198.8948	$198.89	$198.90	$198.90
Purchase #6	$138.47	5.793%	$146.4916	$146.49	$146.50	$146.50
Purchase #7	$91.68	7.413%	$98.4762	$98.48	$98.50	$98.50
7 purchase totals =	$765.05		$821.9889	$821.98	$822.00	$822.10