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	$36.29	10.545%	$40.1168	$40.12	$40.10	$40.10
Purchase #2	$77.53	3.301%	$80.0893	$80.09	$80.10	$80.10
Purchase #3	$167.32	3.286%	$172.8181	$172.82	$172.80	$172.80
Purchase #4	$138.49	9.727%	$151.9609	$151.96	$151.95	$152.00
Purchase #5	$11.98	10.850%	$13.2798	$13.28	$13.30	$13.30
Purchase #6	$169.40	9.640%	$185.7302	$185.73	$185.75	$185.70
Purchase #7	$231.46	13.758%	$263.3043	$263.30	$263.30	$263.30
7 purchase totals =	$832.47		$907.2994	$907.30	$907.30	$907.30