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	$214.72	9.624%	$235.3847	$235.38	$235.40	$235.40
Purchase #2	$244.31	10.360%	$269.6205	$269.62	$269.60	$269.60
Purchase #3	$99.61	4.544%	$104.1363	$104.14	$104.15	$104.10
Purchase #4	$100.98	7.471%	$108.5242	$108.52	$108.50	$108.50
Purchase #5	$26.47	5.160%	$27.8359	$27.84	$27.85	$27.80
Purchase #6	$242.76	8.837%	$264.2127	$264.21	$264.20	$264.20
Purchase #7	$111.82	10.143%	$123.1619	$123.16	$123.15	$123.20
7 purchase totals =	$1,040.67		$1,132.8762	$1,132.87	$1,132.85	$1,132.80