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	$219.28	5.739%	$231.8645	$231.86	$231.85	$231.90
Purchase #2	$127.25	3.455%	$131.6465	$131.65	$131.65	$131.60
Purchase #3	$97.32	11.103%	$108.1254	$108.13	$108.15	$108.10
Purchase #4	$70.26	13.864%	$80.0008	$80.00	$80.00	$80.00
Purchase #5	$222.75	5.478%	$234.9522	$234.95	$234.95	$235.00
Purchase #6	$93.58	6.674%	$99.8255	$99.83	$99.85	$99.80
Purchase #7	$83.42	10.865%	$92.4836	$92.48	$92.50	$92.50
7 purchase totals =	$913.86		$978.8985	$978.90	$978.95	$978.90