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	$168.57	10.657%	$186.5345	$186.53	$186.55	$186.50
Purchase #2	$184.35	6.562%	$196.447	$196.45	$196.45	$196.40
Purchase #3	$6.55	11.634%	$7.312	$7.31	$7.30	$7.30
Purchase #4	$137.58	3.717%	$142.6938	$142.69	$142.70	$142.70
Purchase #5	$9.48	7.686%	$10.2086	$10.21	$10.20	$10.20
Purchase #6	$151.59	13.198%	$171.5968	$171.60	$171.60	$171.60
Purchase #7	$176.69	11.255%	$196.5765	$196.58	$196.60	$196.60
7 purchase totals =	$834.81		$911.3692	$911.37	$911.40	$911.30