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	$127.69	13.213%	$144.5617	$144.56	$144.55	$144.60
Purchase #2	$99.73	4.773%	$104.4901	$104.49	$104.50	$104.50
Purchase #3	$93.80	7.151%	$100.5076	$100.51	$100.50	$100.50
Purchase #4	$156.94	11.745%	$175.3726	$175.37	$175.35	$175.40
Purchase #5	$88.83	13.709%	$101.0077	$101.01	$101.00	$101.00
Purchase #6	$46.93	7.617%	$50.5047	$50.50	$50.50	$50.50
Purchase #7	$184.94	10.377%	$204.1312	$204.13	$204.15	$204.10
7 purchase totals =	$798.86		$880.5756	$880.57	$880.55	$880.60