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	$132.57	12.183%	$148.721	$148.72	$148.70	$148.70
Purchase #2	$118.32	4.867%	$124.0786	$124.08	$124.10	$124.10
Purchase #3	$130.47	9.280%	$142.5776	$142.58	$142.60	$142.60
Purchase #4	$34.31	8.783%	$37.3234	$37.32	$37.30	$37.30
Purchase #5	$147.40	7.336%	$158.2133	$158.21	$158.20	$158.20
Purchase #6	$65.69	7.461%	$70.5911	$70.59	$70.60	$70.60
Purchase #7	$157.58	10.622%	$174.3181	$174.32	$174.30	$174.30
7 purchase totals =	$786.34		$855.8231	$855.82	$855.80	$855.80