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	$72.45	13.822%	$82.464	$82.46	$82.45	$82.50
Purchase #2	$28.60	3.698%	$29.6576	$29.66	$29.65	$29.70
Purchase #3	$121.29	9.496%	$132.8077	$132.81	$132.80	$132.80
Purchase #4	$170.94	5.577%	$180.4733	$180.47	$180.45	$180.50
Purchase #5	$193.78	8.159%	$209.5905	$209.59	$209.60	$209.60
Purchase #6	$85.89	7.764%	$92.5585	$92.56	$92.55	$92.60
Purchase #7	$112.38	13.138%	$127.1445	$127.14	$127.15	$127.10
7 purchase totals =	$785.33		$854.6961	$854.69	$854.65	$854.80