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	$116.80	13.127%	$132.1323	$132.13	$132.15	$132.10
Purchase #2	$71.62	9.766%	$78.6144	$78.61	$78.60	$78.60
Purchase #3	$79.60	11.123%	$88.4539	$88.45	$88.45	$88.50
Purchase #4	$196.86	6.478%	$209.6126	$209.61	$209.60	$209.60
Purchase #5	$199.85	12.666%	$225.163	$225.16	$225.15	$225.20
Purchase #6	$226.28	10.331%	$249.657	$249.66	$249.65	$249.70
Purchase #7	$220.94	3.546%	$228.7745	$228.77	$228.75	$228.80
7 purchase totals =	$1,111.95		$1,212.4077	$1,212.39	$1,212.35	$1,212.50