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	$144.30	5.633%	$152.4284	$152.43	$152.45	$152.40
Purchase #2	$203.58	9.224%	$222.3582	$222.36	$222.35	$222.40
Purchase #3	$37.38	10.128%	$41.1658	$41.17	$41.15	$41.20
Purchase #4	$49.29	8.496%	$53.4777	$53.48	$53.50	$53.50
Purchase #5	$180.64	7.729%	$194.6017	$194.60	$194.60	$194.60
Purchase #6	$141.49	12.172%	$158.7122	$158.71	$158.70	$158.70
Purchase #7	$193.76	7.674%	$208.6291	$208.63	$208.65	$208.60
7 purchase totals =	$950.44		$1,031.3731	$1,031.38	$1,031.40	$1,031.40