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	$95.66	10.253%	$105.468	$105.47	$105.45	$105.50
Purchase #2	$64.59	7.434%	$69.3916	$69.39	$69.40	$69.40
Purchase #3	$128.30	11.811%	$143.4535	$143.45	$143.45	$143.50
Purchase #4	$156.49	10.237%	$172.5099	$172.51	$172.50	$172.50
Purchase #5	$32.41	6.446%	$34.4991	$34.50	$34.50	$34.50
Purchase #6	$65.73	11.849%	$73.5183	$73.52	$73.50	$73.50
Purchase #7	$56.27	8.337%	$60.9612	$60.96	$60.95	$61.00
7 purchase totals =	$599.45		$659.8016	$659.80	$659.75	$659.90