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	$37.82	8.737%	$41.1243	$41.12	$41.10	$41.10
Purchase #2	$196.78	11.726%	$219.8544	$219.85	$219.85	$219.90
Purchase #3	$235.50	8.475%	$255.4586	$255.46	$255.45	$255.50
Purchase #4	$55.67	8.178%	$60.2227	$60.22	$60.20	$60.20
Purchase #5	$87.53	3.585%	$90.668	$90.67	$90.65	$90.70
Purchase #6	$53.98	11.859%	$60.3815	$60.38	$60.40	$60.40
Purchase #7	$151.49	6.236%	$160.9369	$160.94	$160.95	$160.90
7 purchase totals =	$818.77		$888.6464	$888.64	$888.60	$888.70