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	$149.30	8.662%	$162.2324	$162.23	$162.25	$162.20
Purchase #2	$111.59	13.721%	$126.9013	$126.90	$126.90	$126.90
Purchase #3	$168.94	10.801%	$187.1872	$187.19	$187.20	$187.20
Purchase #4	$157.76	5.376%	$166.2412	$166.24	$166.25	$166.20
Purchase #5	$45.89	4.833%	$48.1079	$48.11	$48.10	$48.10
Purchase #6	$191.60	6.156%	$203.3949	$203.39	$203.40	$203.40
Purchase #7	$244.53	4.238%	$254.8932	$254.89	$254.90	$254.90
7 purchase totals =	$1,069.61		$1,148.9581	$1,148.95	$1,149.00	$1,148.90