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	$116.56	10.298%	$128.5633	$128.56	$128.55	$128.60
Purchase #2	$95.68	10.383%	$105.6145	$105.61	$105.60	$105.60
Purchase #3	$96.75	3.692%	$100.322	$100.32	$100.30	$100.30
Purchase #4	$18.30	3.262%	$18.8969	$18.90	$18.90	$18.90
Purchase #5	$113.25	10.820%	$125.5037	$125.50	$125.50	$125.50
Purchase #6	$215.27	13.636%	$244.6242	$244.62	$244.60	$244.60
Purchase #7	$133.42	4.219%	$139.049	$139.05	$139.05	$139.00
7 purchase totals =	$789.23		$862.5736	$862.56	$862.50	$862.50