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	$221.60	10.229%	$244.2675	$244.27	$244.25	$244.30
Purchase #2	$110.54	8.148%	$119.5468	$119.55	$119.55	$119.50
Purchase #3	$54.85	10.136%	$60.4096	$60.41	$60.40	$60.40
Purchase #4	$250.64	5.734%	$265.0117	$265.01	$265.00	$265.00
Purchase #5	$20.34	4.247%	$21.2038	$21.20	$21.20	$21.20
Purchase #6	$186.88	9.779%	$205.155	$205.16	$205.15	$205.20
Purchase #7	$158.59	8.640%	$172.2922	$172.29	$172.30	$172.30
7 purchase totals =	$1,003.44		$1,087.8866	$1,087.89	$1,087.85	$1,087.90