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	$151.26	9.686%	$165.911	$165.91	$165.90	$165.90
Purchase #2	$166.97	9.157%	$182.2594	$182.26	$182.25	$182.30
Purchase #3	$72.57	11.321%	$80.7856	$80.79	$80.80	$80.80
Purchase #4	$41.67	9.395%	$45.5849	$45.58	$45.60	$45.60
Purchase #5	$117.55	3.142%	$121.2434	$121.24	$121.25	$121.20
Purchase #6	$32.51	12.227%	$36.485	$36.49	$36.50	$36.50
Purchase #7	$100.65	11.124%	$111.8463	$111.85	$111.85	$111.80
7 purchase totals =	$683.18		$744.1156	$744.12	$744.15	$744.10