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	$98.61	5.117%	$103.6559	$103.66	$103.65	$103.70
Purchase #2	$73.95	11.126%	$82.1777	$82.18	$82.20	$82.20
Purchase #3	$143.42	5.709%	$151.6078	$151.61	$151.60	$151.60
Purchase #4	$158.96	12.697%	$179.1432	$179.14	$179.15	$179.10
Purchase #5	$242.64	5.160%	$255.1602	$255.16	$255.15	$255.20
Purchase #6	$215.96	12.348%	$242.6267	$242.63	$242.65	$242.60
Purchase #7	$179.77	6.194%	$190.905	$190.91	$190.90	$190.90
7 purchase totals =	$1,113.31		$1,205.2765	$1,205.29	$1,205.30	$1,205.30