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	$249.31	4.447%	$260.3968	$260.40	$260.40	$260.40
Purchase #2	$232.50	13.135%	$263.0389	$263.04	$263.05	$263.00
Purchase #3	$244.76	7.109%	$262.16	$262.16	$262.15	$262.20
Purchase #4	$146.51	10.871%	$162.4371	$162.44	$162.45	$162.40
Purchase #5	$46.43	13.125%	$52.5239	$52.52	$52.50	$52.50
Purchase #6	$149.37	5.819%	$158.0618	$158.06	$158.05	$158.10
Purchase #7	$50.56	8.576%	$54.896	$54.90	$54.90	$54.90
7 purchase totals =	$1,119.44		$1,213.5145	$1,213.52	$1,213.50	$1,213.50