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	$61.61	9.343%	$67.3662	$67.37	$67.35	$67.40
Purchase #2	$127.28	4.332%	$132.7938	$132.79	$132.80	$132.80
Purchase #3	$167.42	9.865%	$183.936	$183.94	$183.95	$183.90
Purchase #4	$57.72	8.318%	$62.5211	$62.52	$62.50	$62.50
Purchase #5	$37.78	11.577%	$42.1538	$42.15	$42.15	$42.20
Purchase #6	$149.74	10.380%	$165.283	$165.28	$165.30	$165.30
Purchase #7	$69.78	5.441%	$73.5767	$73.58	$73.60	$73.60
7 purchase totals =	$671.33		$727.6306	$727.63	$727.65	$727.70