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	$172.45	6.722%	$184.0421	$184.04	$184.05	$184.00
Purchase #2	$225.59	7.385%	$242.2498	$242.25	$242.25	$242.20
Purchase #3	$93.44	6.263%	$99.2921	$99.29	$99.30	$99.30
Purchase #4	$49.51	11.329%	$55.119	$55.12	$55.10	$55.10
Purchase #5	$112.33	13.570%	$127.5732	$127.57	$127.55	$127.60
Purchase #6	$108.42	7.493%	$116.5439	$116.54	$116.55	$116.50
Purchase #7	$48.67	6.243%	$51.7085	$51.71	$51.70	$51.70
7 purchase totals =	$810.41		$876.5286	$876.52	$876.50	$876.40