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	$165.46	4.330%	$172.6244	$172.62	$172.60	$172.60
Purchase #2	$192.93	8.613%	$209.5471	$209.55	$209.55	$209.50
Purchase #3	$113.77	13.218%	$128.8081	$128.81	$128.80	$128.80
Purchase #4	$208.29	5.824%	$220.4208	$220.42	$220.40	$220.40
Purchase #5	$241.35	9.810%	$265.0264	$265.03	$265.05	$265.00
Purchase #6	$43.80	9.476%	$47.9505	$47.95	$47.95	$48.00
Purchase #7	$99.68	12.261%	$111.9018	$111.90	$111.90	$111.90
7 purchase totals =	$1,065.28		$1,156.2791	$1,156.28	$1,156.25	$1,156.20