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	$51.65	3.306%	$53.3575	$53.36	$53.35	$53.40
Purchase #2	$85.28	6.684%	$90.9801	$90.98	$91.00	$91.00
Purchase #3	$173.96	9.299%	$190.1365	$190.14	$190.15	$190.10
Purchase #4	$95.81	4.623%	$100.2393	$100.24	$100.25	$100.20
Purchase #5	$194.44	12.763%	$219.2564	$219.26	$219.25	$219.30
Purchase #6	$116.60	13.799%	$132.6896	$132.69	$132.70	$132.70
Purchase #7	$149.42	10.389%	$164.9432	$164.94	$164.95	$164.90
7 purchase totals =	$867.16		$951.6026	$951.61	$951.65	$951.60