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	$134.35	7.634%	$144.6063	$144.61	$144.60	$144.60
Purchase #2	$198.58	7.404%	$213.2829	$213.28	$213.30	$213.30
Purchase #3	$71.84	4.303%	$74.9313	$74.93	$74.95	$74.90
Purchase #4	$234.60	5.510%	$247.5265	$247.53	$247.55	$247.50
Purchase #5	$238.81	3.680%	$247.5982	$247.60	$247.60	$247.60
Purchase #6	$19.54	5.457%	$20.6063	$20.61	$20.60	$20.60
Purchase #7	$118.33	10.343%	$130.5689	$130.57	$130.55	$130.60
7 purchase totals =	$1,016.05		$1,079.1204	$1,079.13	$1,079.15	$1,079.10