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	$82.76	3.446%	$85.6119	$85.61	$85.60	$85.60
Purchase #2	$157.99	13.733%	$179.6868	$179.69	$179.70	$179.70
Purchase #3	$67.31	7.526%	$72.3758	$72.38	$72.40	$72.40
Purchase #4	$85.85	12.140%	$96.2722	$96.27	$96.25	$96.30
Purchase #5	$25.77	11.445%	$28.7194	$28.72	$28.70	$28.70
Purchase #6	$132.26	8.352%	$143.3064	$143.31	$143.30	$143.30
Purchase #7	$60.29	12.195%	$67.6424	$67.64	$67.65	$67.60
7 purchase totals =	$612.23		$673.6149	$673.62	$673.60	$673.60