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	$31.52	4.116%	$32.8174	$32.82	$32.80	$32.80
Purchase #2	$15.54	7.765%	$16.7467	$16.75	$16.75	$16.70
Purchase #3	$65.70	10.501%	$72.5992	$72.60	$72.60	$72.60
Purchase #4	$152.26	13.449%	$172.7374	$172.74	$172.75	$172.70
Purchase #5	$75.66	8.535%	$82.1176	$82.12	$82.10	$82.10
Purchase #6	$73.54	10.614%	$81.3455	$81.35	$81.35	$81.30
Purchase #7	$54.52	5.294%	$57.4063	$57.41	$57.40	$57.40
7 purchase totals =	$468.74		$515.7701	$515.79	$515.75	$515.60