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	$197.83	4.762%	$207.2507	$207.25	$207.25	$207.30
Purchase #2	$37.68	11.851%	$42.1455	$42.15	$42.15	$42.10
Purchase #3	$85.49	6.288%	$90.8656	$90.87	$90.85	$90.90
Purchase #4	$219.94	3.354%	$227.3168	$227.32	$227.30	$227.30
Purchase #5	$34.37	8.624%	$37.3341	$37.33	$37.35	$37.30
Purchase #6	$229.86	6.260%	$244.2492	$244.25	$244.25	$244.20
Purchase #7	$15.52	4.863%	$16.2747	$16.27	$16.25	$16.30
7 purchase totals =	$820.69		$865.4366	$865.44	$865.40	$865.40