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	$209.98	3.526%	$217.3839	$217.38	$217.40	$217.40
Purchase #2	$173.91	10.483%	$192.141	$192.14	$192.15	$192.10
Purchase #3	$85.92	4.625%	$89.8938	$89.89	$89.90	$89.90
Purchase #4	$44.82	8.769%	$48.7503	$48.75	$48.75	$48.80
Purchase #5	$245.51	12.190%	$275.4377	$275.44	$275.45	$275.40
Purchase #6	$92.77	13.608%	$105.3941	$105.39	$105.40	$105.40
Purchase #7	$75.75	7.628%	$81.5282	$81.53	$81.55	$81.50
7 purchase totals =	$928.66		$1,010.5290	$1,010.52	$1,010.60	$1,010.50