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	$203.72	11.559%	$227.268	$227.27	$227.25	$227.30
Purchase #2	$115.52	4.555%	$120.7819	$120.78	$120.80	$120.80
Purchase #3	$136.29	3.644%	$141.2564	$141.26	$141.25	$141.30
Purchase #4	$132.91	13.735%	$151.1652	$151.17	$151.15	$151.20
Purchase #5	$79.98	3.539%	$82.8105	$82.81	$82.80	$82.80
Purchase #6	$219.66	5.431%	$231.5897	$231.59	$231.60	$231.60
Purchase #7	$167.36	3.396%	$173.0435	$173.04	$173.05	$173.00
7 purchase totals =	$1,055.44		$1,127.9152	$1,127.92	$1,127.90	$1,128.00