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	$144.48	4.736%	$151.3226	$151.32	$151.30	$151.30
Purchase #2	$47.50	10.518%	$52.4961	$52.50	$52.50	$52.50
Purchase #3	$140.37	4.158%	$146.2066	$146.21	$146.20	$146.20
Purchase #4	$12.25	11.431%	$13.6503	$13.65	$13.65	$13.70
Purchase #5	$95.92	4.350%	$100.0925	$100.09	$100.10	$100.10
Purchase #6	$65.72	13.494%	$74.5883	$74.59	$74.60	$74.60
Purchase #7	$106.25	9.511%	$116.3554	$116.36	$116.35	$116.40
7 purchase totals =	$612.49		$654.7118	$654.72	$654.70	$654.80