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	$162.39	6.252%	$172.5426	$172.54	$172.55	$172.50
Purchase #2	$176.73	4.708%	$185.0504	$185.05	$185.05	$185.10
Purchase #3	$105.92	9.585%	$116.0724	$116.07	$116.05	$116.10
Purchase #4	$246.54	3.175%	$254.3676	$254.37	$254.35	$254.40
Purchase #5	$143.43	5.288%	$151.0146	$151.01	$151.00	$151.00
Purchase #6	$205.76	9.551%	$225.4121	$225.41	$225.40	$225.40
Purchase #7	$93.62	8.832%	$101.8885	$101.89	$101.90	$101.90
7 purchase totals =	$1,134.39		$1,206.3482	$1,206.34	$1,206.30	$1,206.40