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	$246.53	11.709%	$275.3962	$275.40	$275.40	$275.40
Purchase #2	$20.56	10.180%	$22.653	$22.65	$22.65	$22.70
Purchase #3	$92.52	9.513%	$101.3214	$101.32	$101.30	$101.30
Purchase #4	$242.28	13.278%	$274.4499	$274.45	$274.45	$274.40
Purchase #5	$81.57	10.301%	$89.9725	$89.97	$89.95	$90.00
Purchase #6	$46.59	5.669%	$49.2312	$49.23	$49.25	$49.20
Purchase #7	$219.56	13.304%	$248.7703	$248.77	$248.75	$248.80
7 purchase totals =	$949.61		$1,061.7945	$1,061.79	$1,061.75	$1,061.80