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	$83.43	10.228%	$91.9632	$91.96	$91.95	$92.00
Purchase #2	$106.77	4.173%	$111.2255	$111.23	$111.25	$111.20
Purchase #3	$149.30	11.639%	$166.677	$166.68	$166.70	$166.70
Purchase #4	$151.53	6.124%	$160.8097	$160.81	$160.80	$160.80
Purchase #5	$132.75	11.163%	$147.5689	$147.57	$147.55	$147.60
Purchase #6	$45.66	13.734%	$51.9309	$51.93	$51.95	$51.90
Purchase #7	$174.52	6.378%	$185.6509	$185.65	$185.65	$185.70
7 purchase totals =	$843.96		$915.8261	$915.83	$915.85	$915.90