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	$209.65	6.369%	$223.0026	$223.00	$223.00	$223.00
Purchase #2	$172.89	9.168%	$188.7406	$188.74	$188.75	$188.70
Purchase #3	$227.72	4.152%	$237.1749	$237.17	$237.15	$237.20
Purchase #4	$167.33	8.482%	$181.5229	$181.52	$181.50	$181.50
Purchase #5	$176.40	11.633%	$196.9206	$196.92	$196.90	$196.90
Purchase #6	$176.49	7.754%	$190.175	$190.18	$190.20	$190.20
Purchase #7	$224.64	7.327%	$241.0994	$241.10	$241.10	$241.10
7 purchase totals =	$1,355.12		$1,458.6360	$1,458.63	$1,458.60	$1,458.60