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	$96.34	9.514%	$105.5058	$105.51	$105.50	$105.50
Purchase #2	$176.47	4.587%	$184.5647	$184.56	$184.55	$184.60
Purchase #3	$58.67	13.254%	$66.4461	$66.45	$66.45	$66.40
Purchase #4	$76.53	7.646%	$82.3815	$82.38	$82.40	$82.40
Purchase #5	$146.77	6.686%	$156.583	$156.58	$156.60	$156.60
Purchase #6	$204.84	7.585%	$220.3771	$220.38	$220.40	$220.40
Purchase #7	$88.66	9.373%	$96.9701	$96.97	$96.95	$97.00
7 purchase totals =	$848.28		$912.8283	$912.83	$912.85	$912.90