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	$138.91	10.552%	$153.5678	$153.57	$153.55	$153.60
Purchase #2	$139.98	3.663%	$145.1075	$145.11	$145.10	$145.10
Purchase #3	$101.73	9.243%	$111.1329	$111.13	$111.15	$111.10
Purchase #4	$96.85	7.141%	$103.7661	$103.77	$103.75	$103.80
Purchase #5	$119.39	8.392%	$129.4092	$129.41	$129.40	$129.40
Purchase #6	$48.66	12.614%	$54.798	$54.80	$54.80	$54.80
Purchase #7	$212.37	11.810%	$237.4509	$237.45	$237.45	$237.50
7 purchase totals =	$857.89		$935.2324	$935.24	$935.20	$935.30