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	$214.33	13.510%	$243.286	$243.29	$243.30	$243.30
Purchase #2	$130.41	10.851%	$144.5608	$144.56	$144.55	$144.60
Purchase #3	$65.81	7.110%	$70.4891	$70.49	$70.50	$70.50
Purchase #4	$6.56	6.700%	$6.9995	$7.00	$7.00	$7.00
Purchase #5	$64.94	3.792%	$67.4025	$67.40	$67.40	$67.40
Purchase #6	$73.78	9.330%	$80.6637	$80.66	$80.65	$80.70
Purchase #7	$172.44	12.544%	$194.0709	$194.07	$194.05	$194.10
7 purchase totals =	$728.27		$807.4725	$807.47	$807.45	$807.60