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	$6.48	12.275%	$7.2754	$7.28	$7.30	$7.30
Purchase #2	$144.83	4.510%	$151.3618	$151.36	$151.35	$151.40
Purchase #3	$246.33	3.860%	$255.8383	$255.84	$255.85	$255.80
Purchase #4	$46.71	4.348%	$48.741	$48.74	$48.75	$48.70
Purchase #5	$223.65	4.209%	$233.0634	$233.06	$233.05	$233.10
Purchase #6	$223.93	13.537%	$254.2434	$254.24	$254.25	$254.20
Purchase #7	$199.65	11.195%	$222.0008	$222.00	$222.00	$222.00
7 purchase totals =	$1,091.58		$1,172.5241	$1,172.52	$1,172.55	$1,172.50