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	$56.41	7.187%	$60.4642	$60.46	$60.45	$60.50
Purchase #2	$158.87	8.642%	$172.5995	$172.60	$172.60	$172.60
Purchase #3	$123.85	10.275%	$136.5756	$136.58	$136.60	$136.60
Purchase #4	$39.59	8.237%	$42.851	$42.85	$42.85	$42.90
Purchase #5	$25.87	13.374%	$29.3299	$29.33	$29.35	$29.30
Purchase #6	$86.38	8.739%	$93.9287	$93.93	$93.95	$93.90
Purchase #7	$104.92	10.714%	$116.1611	$116.16	$116.15	$116.20
7 purchase totals =	$595.89		$651.9100	$651.91	$651.95	$652.00