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	$140.80	10.462%	$155.5305	$155.53	$155.55	$155.50
Purchase #2	$25.84	10.642%	$28.5899	$28.59	$28.60	$28.60
Purchase #3	$147.51	4.295%	$153.8456	$153.85	$153.85	$153.80
Purchase #4	$33.80	6.300%	$35.9294	$35.93	$35.95	$35.90
Purchase #5	$18.84	7.526%	$20.2579	$20.26	$20.25	$20.30
Purchase #6	$27.68	9.341%	$30.2656	$30.27	$30.25	$30.30
Purchase #7	$25.48	11.718%	$28.4657	$28.47	$28.45	$28.50
7 purchase totals =	$419.95		$452.8846	$452.90	$452.90	$452.90