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	$213.69	13.648%	$242.8544	$242.85	$242.85	$242.90
Purchase #2	$248.89	11.856%	$278.3984	$278.40	$278.40	$278.40
Purchase #3	$12.57	10.168%	$13.8481	$13.85	$13.85	$13.80
Purchase #4	$146.91	4.302%	$153.2301	$153.23	$153.25	$153.20
Purchase #5	$145.30	5.663%	$153.5283	$153.53	$153.55	$153.50
Purchase #6	$100.45	5.496%	$105.9707	$105.97	$105.95	$106.00
Purchase #7	$146.93	11.154%	$163.3186	$163.32	$163.30	$163.30
7 purchase totals =	$1,014.74		$1,111.1486	$1,111.15	$1,111.15	$1,111.10