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	$12.39	13.465%	$14.0583	$14.06	$14.05	$14.10
Purchase #2	$229.49	13.539%	$260.5607	$260.56	$260.55	$260.60
Purchase #3	$85.34	5.487%	$90.0226	$90.02	$90.00	$90.00
Purchase #4	$203.29	3.376%	$210.1531	$210.15	$210.15	$210.20
Purchase #5	$145.60	3.720%	$151.0163	$151.02	$151.00	$151.00
Purchase #6	$54.67	11.612%	$61.0183	$61.02	$61.00	$61.00
Purchase #7	$42.54	9.454%	$46.5617	$46.56	$46.55	$46.60
7 purchase totals =	$773.32		$833.3910	$833.39	$833.30	$833.50