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	$158.51	9.173%	$173.0501	$173.05	$173.05	$173.10
Purchase #2	$208.55	4.807%	$218.575	$218.58	$218.60	$218.60
Purchase #3	$83.33	3.200%	$85.9966	$86.00	$86.00	$86.00
Purchase #4	$140.30	8.386%	$152.0656	$152.07	$152.05	$152.10
Purchase #5	$28.40	9.565%	$31.1165	$31.12	$31.10	$31.10
Purchase #6	$244.85	13.665%	$278.3088	$278.31	$278.30	$278.30
Purchase #7	$217.40	5.403%	$229.1461	$229.15	$229.15	$229.10
7 purchase totals =	$1,081.34		$1,168.2587	$1,168.28	$1,168.25	$1,168.30