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	$36.44	5.523%	$38.4526	$38.45	$38.45	$38.50
Purchase #2	$104.69	6.203%	$111.1839	$111.18	$111.20	$111.20
Purchase #3	$51.38	5.136%	$54.0189	$54.02	$54.00	$54.00
Purchase #4	$127.53	4.104%	$132.7638	$132.76	$132.75	$132.80
Purchase #5	$58.59	12.343%	$65.8218	$65.82	$65.80	$65.80
Purchase #6	$117.91	7.717%	$127.0091	$127.01	$127.00	$127.00
Purchase #7	$69.43	5.420%	$73.1931	$73.19	$73.20	$73.20
7 purchase totals =	$565.97		$602.4432	$602.43	$602.40	$602.50