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	$132.44	9.492%	$145.0112	$145.01	$145.00	$145.00
Purchase #2	$57.54	12.158%	$64.5357	$64.54	$64.55	$64.50
Purchase #3	$221.87	3.338%	$229.276	$229.28	$229.30	$229.30
Purchase #4	$64.84	10.645%	$71.7422	$71.74	$71.75	$71.70
Purchase #5	$34.71	13.186%	$39.2869	$39.29	$39.30	$39.30
Purchase #6	$65.32	13.477%	$74.1232	$74.12	$74.10	$74.10
Purchase #7	$150.31	6.807%	$160.5416	$160.54	$160.55	$160.50
7 purchase totals =	$727.03		$784.5168	$784.52	$784.55	$784.40