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	$233.46	3.452%	$241.519	$241.52	$241.50	$241.50
Purchase #2	$76.73	6.329%	$81.5862	$81.59	$81.60	$81.60
Purchase #3	$33.43	8.456%	$36.2568	$36.26	$36.25	$36.30
Purchase #4	$14.92	5.378%	$15.7224	$15.72	$15.70	$15.70
Purchase #5	$247.37	6.541%	$263.5505	$263.55	$263.55	$263.60
Purchase #6	$83.68	6.559%	$89.1686	$89.17	$89.15	$89.20
Purchase #7	$151.32	3.565%	$156.7146	$156.71	$156.70	$156.70
7 purchase totals =	$840.91		$884.5181	$884.52	$884.45	$884.60