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	$192.77	13.326%	$218.4585	$218.46	$218.45	$218.50
Purchase #2	$7.37	6.641%	$7.8594	$7.86	$7.85	$7.90
Purchase #3	$240.83	5.574%	$254.2539	$254.25	$254.25	$254.30
Purchase #4	$122.75	3.669%	$127.2537	$127.25	$127.25	$127.30
Purchase #5	$158.72	10.103%	$174.7555	$174.76	$174.75	$174.80
Purchase #6	$8.30	9.199%	$9.0635	$9.06	$9.05	$9.10
Purchase #7	$99.69	3.582%	$103.2609	$103.26	$103.25	$103.30
7 purchase totals =	$830.43		$894.9054	$894.90	$894.85	$895.20