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	$66.39	9.824%	$72.9122	$72.91	$72.90	$72.90
Purchase #2	$143.41	5.606%	$151.4496	$151.45	$151.45	$151.40
Purchase #3	$68.60	7.554%	$73.782	$73.78	$73.80	$73.80
Purchase #4	$63.50	6.830%	$67.8371	$67.84	$67.85	$67.80
Purchase #5	$202.32	6.180%	$214.8234	$214.82	$214.80	$214.80
Purchase #6	$90.82	10.769%	$100.6004	$100.60	$100.60	$100.60
Purchase #7	$12.58	9.386%	$13.7608	$13.76	$13.75	$13.80
7 purchase totals =	$647.62		$695.1655	$695.16	$695.15	$695.10