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	$224.68	6.209%	$238.6304	$238.63	$238.65	$238.60
Purchase #2	$173.46	9.310%	$189.6091	$189.61	$189.60	$189.60
Purchase #3	$183.76	5.241%	$193.3909	$193.39	$193.40	$193.40
Purchase #4	$50.89	4.392%	$53.1251	$53.13	$53.15	$53.10
Purchase #5	$233.90	9.375%	$255.8281	$255.83	$255.85	$255.80
Purchase #6	$61.78	9.823%	$67.8486	$67.85	$67.85	$67.80
Purchase #7	$176.66	10.828%	$195.7887	$195.79	$195.80	$195.80
7 purchase totals =	$1,105.13		$1,194.2209	$1,194.23	$1,194.30	$1,194.10