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	$138.33	13.433%	$156.9119	$156.91	$156.90	$156.90
Purchase #2	$155.83	11.160%	$173.2206	$173.22	$173.20	$173.20
Purchase #3	$51.64	5.380%	$54.4182	$54.42	$54.40	$54.40
Purchase #4	$90.91	9.445%	$99.4964	$99.50	$99.50	$99.50
Purchase #5	$202.52	10.560%	$223.9061	$223.91	$223.90	$223.90
Purchase #6	$71.63	9.602%	$78.5079	$78.51	$78.50	$78.50
Purchase #7	$130.28	6.332%	$138.5293	$138.53	$138.55	$138.50
7 purchase totals =	$841.14		$924.9904	$925.00	$924.95	$924.90