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	$217.25	12.290%	$243.95	$243.95	$243.95	$244.00
Purchase #2	$141.94	5.651%	$149.961	$149.96	$149.95	$150.00
Purchase #3	$229.58	6.406%	$244.2869	$244.29	$244.30	$244.30
Purchase #4	$52.92	3.579%	$54.814	$54.81	$54.80	$54.80
Purchase #5	$130.89	10.777%	$144.996	$145.00	$145.00	$145.00
Purchase #6	$152.51	9.540%	$167.0595	$167.06	$167.05	$167.10
Purchase #7	$80.68	10.654%	$89.2756	$89.28	$89.30	$89.30
7 purchase totals =	$1,005.77		$1,094.3430	$1,094.35	$1,094.35	$1,094.50