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	$173.49	6.471%	$184.7165	$184.72	$184.70	$184.70
Purchase #2	$170.61	11.482%	$190.1994	$190.20	$190.20	$190.20
Purchase #3	$200.43	10.305%	$221.0843	$221.08	$221.10	$221.10
Purchase #4	$243.63	4.539%	$254.6884	$254.69	$254.70	$254.70
Purchase #5	$175.49	13.449%	$199.0917	$199.09	$199.10	$199.10
Purchase #6	$59.42	3.408%	$61.445	$61.45	$61.45	$61.40
Purchase #7	$201.75	4.222%	$210.2679	$210.27	$210.25	$210.30
7 purchase totals =	$1,224.82		$1,321.4932	$1,321.50	$1,321.50	$1,321.50