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	$211.46	11.393%	$235.5516	$235.55	$235.55	$235.60
Purchase #2	$168.93	4.729%	$176.9187	$176.92	$176.90	$176.90
Purchase #3	$105.84	5.212%	$111.3564	$111.36	$111.35	$111.40
Purchase #4	$29.51	13.850%	$33.5971	$33.60	$33.60	$33.60
Purchase #5	$209.73	11.191%	$233.2009	$233.20	$233.20	$233.20
Purchase #6	$13.45	5.313%	$14.1646	$14.16	$14.15	$14.20
Purchase #7	$52.53	5.569%	$55.4554	$55.46	$55.45	$55.50
7 purchase totals =	$791.45		$860.2447	$860.25	$860.20	$860.40