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	$182.67	7.321%	$196.0433	$196.04	$196.05	$196.00
Purchase #2	$92.74	10.356%	$102.3442	$102.34	$102.35	$102.30
Purchase #3	$155.76	13.328%	$176.5197	$176.52	$176.50	$176.50
Purchase #4	$75.64	10.256%	$83.3976	$83.40	$83.40	$83.40
Purchase #5	$106.37	11.329%	$118.4207	$118.42	$118.40	$118.40
Purchase #6	$147.62	13.225%	$167.1427	$167.14	$167.15	$167.10
Purchase #7	$86.72	6.585%	$92.4305	$92.43	$92.45	$92.40
7 purchase totals =	$847.52		$936.2987	$936.29	$936.30	$936.10