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	$157.92	6.345%	$167.94	$167.94	$167.95	$167.90
Purchase #2	$113.33	12.142%	$127.0905	$127.09	$127.10	$127.10
Purchase #3	$113.63	11.190%	$126.3452	$126.35	$126.35	$126.30
Purchase #4	$34.30	12.257%	$38.5042	$38.50	$38.50	$38.50
Purchase #5	$65.25	12.320%	$73.2888	$73.29	$73.30	$73.30
Purchase #6	$158.83	4.311%	$165.6772	$165.68	$165.70	$165.70
Purchase #7	$54.72	4.360%	$57.1058	$57.11	$57.10	$57.10
7 purchase totals =	$697.98		$755.9517	$755.96	$756.00	$755.90