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	$114.75	10.212%	$126.4683	$126.47	$126.45	$126.50
Purchase #2	$18.37	9.607%	$20.1348	$20.13	$20.15	$20.10
Purchase #3	$158.74	4.788%	$166.3405	$166.34	$166.35	$166.30
Purchase #4	$92.31	13.328%	$104.6131	$104.61	$104.60	$104.60
Purchase #5	$7.70	6.103%	$8.1699	$8.17	$8.15	$8.20
Purchase #6	$98.40	5.675%	$103.9842	$103.98	$104.00	$104.00
Purchase #7	$86.51	3.683%	$89.6962	$89.70	$89.70	$89.70
7 purchase totals =	$576.78		$619.4070	$619.40	$619.40	$619.40