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	$144.65	5.230%	$152.2152	$152.22	$152.20	$152.20
Purchase #2	$124.99	6.254%	$132.8069	$132.81	$132.80	$132.80
Purchase #3	$185.80	10.403%	$205.1288	$205.13	$205.15	$205.10
Purchase #4	$157.78	6.309%	$167.7343	$167.73	$167.75	$167.70
Purchase #5	$90.31	13.273%	$102.2968	$102.30	$102.30	$102.30
Purchase #6	$64.90	11.573%	$72.4109	$72.41	$72.40	$72.40
Purchase #7	$106.89	9.412%	$116.9505	$116.95	$116.95	$117.00
7 purchase totals =	$875.32		$949.5434	$949.55	$949.55	$949.50