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	$158.85	9.499%	$173.9392	$173.94	$173.95	$173.90
Purchase #2	$41.50	4.543%	$43.3853	$43.39	$43.40	$43.40
Purchase #3	$199.61	11.760%	$223.0841	$223.08	$223.10	$223.10
Purchase #4	$183.98	3.346%	$190.136	$190.14	$190.15	$190.10
Purchase #5	$148.33	6.140%	$157.4375	$157.44	$157.45	$157.40
Purchase #6	$135.73	13.275%	$153.7482	$153.75	$153.75	$153.70
Purchase #7	$120.34	6.251%	$127.8625	$127.86	$127.85	$127.90
7 purchase totals =	$988.34		$1,069.5928	$1,069.60	$1,069.65	$1,069.50