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	$55.74	6.367%	$59.289	$59.29	$59.30	$59.30
Purchase #2	$95.36	4.534%	$99.6836	$99.68	$99.70	$99.70
Purchase #3	$99.47	13.339%	$112.7383	$112.74	$112.75	$112.70
Purchase #4	$139.58	11.197%	$155.2088	$155.21	$155.20	$155.20
Purchase #5	$241.82	10.165%	$266.401	$266.40	$266.40	$266.40
Purchase #6	$224.39	12.451%	$252.3288	$252.33	$252.35	$252.30
Purchase #7	$157.98	5.175%	$166.1555	$166.16	$166.15	$166.20
7 purchase totals =	$1,014.34		$1,111.8050	$1,111.81	$1,111.85	$1,111.80