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	$130.92	10.103%	$144.1468	$144.15	$144.15	$144.10
Purchase #2	$241.38	12.267%	$270.9901	$270.99	$271.00	$271.00
Purchase #3	$235.42	12.231%	$264.2142	$264.21	$264.20	$264.20
Purchase #4	$127.56	7.154%	$136.6856	$136.69	$136.70	$136.70
Purchase #5	$87.66	3.632%	$90.8438	$90.84	$90.85	$90.80
Purchase #6	$141.87	13.104%	$160.4606	$160.46	$160.45	$160.50
Purchase #7	$39.46	5.572%	$41.6587	$41.66	$41.65	$41.70
7 purchase totals =	$1,004.27		$1,108.9998	$1,109.00	$1,109.00	$1,109.00