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	$165.50	3.695%	$171.6152	$171.62	$171.60	$171.60
Purchase #2	$43.68	11.270%	$48.6027	$48.60	$48.60	$48.60
Purchase #3	$183.81	4.665%	$192.3847	$192.38	$192.40	$192.40
Purchase #4	$160.90	7.286%	$172.6232	$172.62	$172.60	$172.60
Purchase #5	$215.26	11.754%	$240.5617	$240.56	$240.55	$240.60
Purchase #6	$59.48	10.575%	$65.77	$65.77	$65.75	$65.80
Purchase #7	$178.79	13.609%	$203.1215	$203.12	$203.10	$203.10
7 purchase totals =	$1,007.42		$1,094.6790	$1,094.67	$1,094.60	$1,094.70