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	$184.91	13.109%	$209.1499	$209.15	$209.15	$209.10
Purchase #2	$225.79	5.456%	$238.1091	$238.11	$238.10	$238.10
Purchase #3	$199.79	6.408%	$212.5925	$212.59	$212.60	$212.60
Purchase #4	$129.68	9.152%	$141.5483	$141.55	$141.55	$141.50
Purchase #5	$205.41	9.624%	$225.1787	$225.18	$225.20	$225.20
Purchase #6	$53.61	11.807%	$59.9397	$59.94	$59.95	$59.90
Purchase #7	$138.57	9.276%	$151.4238	$151.42	$151.40	$151.40
7 purchase totals =	$1,137.76		$1,237.9420	$1,237.94	$1,237.95	$1,237.80