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	$117.44	10.211%	$129.4318	$129.43	$129.45	$129.40
Purchase #2	$154.38	7.391%	$165.7902	$165.79	$165.80	$165.80
Purchase #3	$41.87	4.223%	$43.6382	$43.64	$43.65	$43.60
Purchase #4	$174.29	3.307%	$180.0538	$180.05	$180.05	$180.10
Purchase #5	$225.81	12.440%	$253.9008	$253.90	$253.90	$253.90
Purchase #6	$242.57	12.196%	$272.1538	$272.15	$272.15	$272.20
Purchase #7	$138.52	9.135%	$151.1738	$151.17	$151.15	$151.20
7 purchase totals =	$1,094.88		$1,196.1424	$1,196.13	$1,196.15	$1,196.20