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	$155.51	13.337%	$176.2504	$176.25	$176.25	$176.30
Purchase #2	$211.70	10.257%	$233.4141	$233.41	$233.40	$233.40
Purchase #3	$172.54	9.408%	$188.7726	$188.77	$188.75	$188.80
Purchase #4	$155.30	5.811%	$164.3245	$164.32	$164.30	$164.30
Purchase #5	$117.42	8.415%	$127.3009	$127.30	$127.30	$127.30
Purchase #6	$22.77	12.162%	$25.5393	$25.54	$25.55	$25.50
Purchase #7	$121.60	12.312%	$136.5714	$136.57	$136.55	$136.60
7 purchase totals =	$956.84		$1,052.1732	$1,052.16	$1,052.10	$1,052.20