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	$53.93	11.520%	$60.1427	$60.14	$60.15	$60.10
Purchase #2	$144.30	9.509%	$158.0215	$158.02	$158.00	$158.00
Purchase #3	$50.92	10.607%	$56.3211	$56.32	$56.30	$56.30
Purchase #4	$130.51	13.179%	$147.7099	$147.71	$147.70	$147.70
Purchase #5	$190.90	3.369%	$197.3314	$197.33	$197.35	$197.30
Purchase #6	$38.48	9.584%	$42.1679	$42.17	$42.15	$42.20
Purchase #7	$31.56	6.174%	$33.5085	$33.51	$33.50	$33.50
7 purchase totals =	$640.60		$695.2030	$695.20	$695.15	$695.10