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	$176.94	5.229%	$186.1922	$186.19	$186.20	$186.20
Purchase #2	$111.92	5.700%	$118.2994	$118.30	$118.30	$118.30
Purchase #3	$210.49	8.762%	$228.9331	$228.93	$228.95	$228.90
Purchase #4	$172.37	13.353%	$195.3866	$195.39	$195.40	$195.40
Purchase #5	$75.25	4.417%	$78.5738	$78.57	$78.55	$78.60
Purchase #6	$111.27	4.192%	$115.9344	$115.93	$115.95	$115.90
Purchase #7	$243.65	7.776%	$262.5962	$262.60	$262.60	$262.60
7 purchase totals =	$1,101.89		$1,185.9157	$1,185.91	$1,185.95	$1,185.90