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	$85.87	5.329%	$90.446	$90.45	$90.45	$90.40
Purchase #2	$214.31	4.481%	$223.9132	$223.91	$223.90	$223.90
Purchase #3	$73.35	6.233%	$77.9219	$77.92	$77.90	$77.90
Purchase #4	$199.29	4.481%	$208.2202	$208.22	$208.20	$208.20
Purchase #5	$187.95	12.666%	$211.7557	$211.76	$211.75	$211.80
Purchase #6	$137.40	3.779%	$142.5923	$142.59	$142.60	$142.60
Purchase #7	$244.51	11.285%	$272.103	$272.10	$272.10	$272.10
7 purchase totals =	$1,142.68		$1,226.9523	$1,226.95	$1,226.90	$1,226.90