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	$107.57	3.747%	$111.6006	$111.60	$111.60	$111.60
Purchase #2	$240.72	6.313%	$255.9167	$255.92	$255.90	$255.90
Purchase #3	$77.69	9.767%	$85.278	$85.28	$85.30	$85.30
Purchase #4	$235.39	11.318%	$262.0314	$262.03	$262.05	$262.00
Purchase #5	$136.77	6.442%	$145.5807	$145.58	$145.60	$145.60
Purchase #6	$26.95	12.556%	$30.3338	$30.33	$30.35	$30.30
Purchase #7	$64.76	6.665%	$69.0763	$69.08	$69.10	$69.10
7 purchase totals =	$889.85		$959.8175	$959.82	$959.90	$959.80