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	$165.37	4.375%	$172.6049	$172.60	$172.60	$172.60
Purchase #2	$104.44	8.470%	$113.2861	$113.29	$113.30	$113.30
Purchase #3	$79.85	13.702%	$90.791	$90.79	$90.80	$90.80
Purchase #4	$52.25	6.130%	$55.4529	$55.45	$55.45	$55.50
Purchase #5	$247.62	4.555%	$258.8991	$258.90	$258.90	$258.90
Purchase #6	$238.28	5.429%	$251.2162	$251.22	$251.20	$251.20
Purchase #7	$85.83	9.657%	$94.1186	$94.12	$94.10	$94.10
7 purchase totals =	$973.64		$1,036.3688	$1,036.37	$1,036.35	$1,036.40