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	$32.97	13.104%	$37.2904	$37.29	$37.30	$37.30
Purchase #2	$104.42	13.755%	$118.783	$118.78	$118.80	$118.80
Purchase #3	$28.40	5.153%	$29.8635	$29.86	$29.85	$29.90
Purchase #4	$33.84	9.573%	$37.0795	$37.08	$37.10	$37.10
Purchase #5	$15.76	9.606%	$17.2739	$17.27	$17.25	$17.30
Purchase #6	$62.61	13.793%	$71.2458	$71.25	$71.25	$71.20
Purchase #7	$52.29	10.329%	$57.691	$57.69	$57.70	$57.70
7 purchase totals =	$330.29		$369.2271	$369.22	$369.25	$369.30