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	$115.57	10.151%	$127.3015	$127.30	$127.30	$127.30
Purchase #2	$26.56	10.847%	$29.441	$29.44	$29.45	$29.40
Purchase #3	$132.59	11.717%	$148.1256	$148.13	$148.15	$148.10
Purchase #4	$72.89	5.654%	$77.0112	$77.01	$77.00	$77.00
Purchase #5	$136.91	13.642%	$155.5873	$155.59	$155.60	$155.60
Purchase #6	$108.36	10.142%	$119.3499	$119.35	$119.35	$119.30
Purchase #7	$63.52	10.844%	$70.4081	$70.41	$70.40	$70.40
7 purchase totals =	$656.40		$727.2246	$727.23	$727.25	$727.10