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	$66.54	8.414%	$72.1387	$72.14	$72.15	$72.10
Purchase #2	$41.49	4.722%	$43.4492	$43.45	$43.45	$43.40
Purchase #3	$248.81	9.440%	$272.2977	$272.30	$272.30	$272.30
Purchase #4	$53.40	12.110%	$59.8667	$59.87	$59.85	$59.90
Purchase #5	$161.58	3.433%	$167.127	$167.13	$167.15	$167.10
Purchase #6	$5.92	12.207%	$6.6427	$6.64	$6.65	$6.60
Purchase #7	$241.42	9.674%	$264.775	$264.78	$264.80	$264.80
7 purchase totals =	$819.16		$886.2970	$886.31	$886.35	$886.20