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	$68.35	4.603%	$71.4962	$71.50	$71.50	$71.50
Purchase #2	$72.68	3.622%	$75.3125	$75.31	$75.30	$75.30
Purchase #3	$170.73	10.571%	$188.7779	$188.78	$188.80	$188.80
Purchase #4	$217.84	11.423%	$242.7239	$242.72	$242.70	$242.70
Purchase #5	$12.40	3.830%	$12.8749	$12.87	$12.85	$12.90
Purchase #6	$18.96	10.810%	$21.0096	$21.01	$21.00	$21.00
Purchase #7	$143.83	3.196%	$148.4268	$148.43	$148.45	$148.40
7 purchase totals =	$704.79		$760.6218	$760.62	$760.60	$760.60