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	$58.35	12.658%	$65.7359	$65.74	$65.75	$65.70
Purchase #2	$105.92	4.857%	$111.0645	$111.06	$111.05	$111.10
Purchase #3	$175.46	12.274%	$196.996	$197.00	$197.00	$197.00
Purchase #4	$93.85	13.446%	$106.4691	$106.47	$106.45	$106.50
Purchase #5	$56.31	3.761%	$58.4278	$58.43	$58.45	$58.40
Purchase #6	$29.50	9.602%	$32.3326	$32.33	$32.35	$32.30
Purchase #7	$51.41	8.790%	$55.9289	$55.93	$55.95	$55.90
7 purchase totals =	$570.80		$626.9548	$626.96	$627.00	$626.90