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	$247.33	6.552%	$263.5351	$263.54	$263.55	$263.50
Purchase #2	$98.45	3.764%	$102.1557	$102.16	$102.15	$102.20
Purchase #3	$124.83	11.818%	$139.5824	$139.58	$139.60	$139.60
Purchase #4	$232.60	9.134%	$253.8457	$253.85	$253.85	$253.80
Purchase #5	$83.60	10.652%	$92.5051	$92.51	$92.50	$92.50
Purchase #6	$9.30	9.233%	$10.1587	$10.16	$10.15	$10.20
Purchase #7	$143.91	10.256%	$158.6694	$158.67	$158.65	$158.70
7 purchase totals =	$940.02		$1,020.4521	$1,020.47	$1,020.45	$1,020.50