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	$109.92	4.764%	$115.1566	$115.16	$115.15	$115.20
Purchase #2	$63.61	13.668%	$72.3042	$72.30	$72.30	$72.30
Purchase #3	$115.44	10.525%	$127.5901	$127.59	$127.60	$127.60
Purchase #4	$126.82	4.538%	$132.5751	$132.58	$132.60	$132.60
Purchase #5	$144.36	7.701%	$155.4772	$155.48	$155.50	$155.50
Purchase #6	$227.50	12.690%	$256.3698	$256.37	$256.35	$256.40
Purchase #7	$244.52	6.854%	$261.2794	$261.28	$261.30	$261.30
7 purchase totals =	$1,032.17		$1,120.7524	$1,120.76	$1,120.80	$1,120.90