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	$241.94	3.363%	$250.0764	$250.08	$250.10	$250.10
Purchase #2	$205.93	13.459%	$233.6461	$233.65	$233.65	$233.60
Purchase #3	$92.61	4.447%	$96.7284	$96.73	$96.75	$96.70
Purchase #4	$219.88	13.810%	$250.2454	$250.25	$250.25	$250.20
Purchase #5	$14.89	10.492%	$16.4523	$16.45	$16.45	$16.50
Purchase #6	$140.91	8.266%	$152.5576	$152.56	$152.55	$152.60
Purchase #7	$104.66	11.725%	$116.9314	$116.93	$116.95	$116.90
7 purchase totals =	$1,020.82		$1,116.6376	$1,116.65	$1,116.70	$1,116.60