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	$104.33	4.102%	$108.6096	$108.61	$108.60	$108.60
Purchase #2	$183.95	11.164%	$204.4862	$204.49	$204.50	$204.50
Purchase #3	$175.88	6.378%	$187.0976	$187.10	$187.10	$187.10
Purchase #4	$207.53	5.774%	$219.5128	$219.51	$219.50	$219.50
Purchase #5	$68.89	5.756%	$72.8553	$72.86	$72.85	$72.90
Purchase #6	$34.61	8.739%	$37.6346	$37.63	$37.65	$37.60
Purchase #7	$152.34	13.217%	$172.4748	$172.47	$172.45	$172.50
7 purchase totals =	$927.53		$1,002.6709	$1,002.67	$1,002.65	$1,002.70