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	$229.31	5.285%	$241.429	$241.43	$241.45	$241.40
Purchase #2	$152.77	6.637%	$162.9093	$162.91	$162.90	$162.90
Purchase #3	$138.86	11.512%	$154.8456	$154.85	$154.85	$154.80
Purchase #4	$51.44	10.142%	$56.657	$56.66	$56.65	$56.70
Purchase #5	$127.65	13.603%	$145.0142	$145.01	$145.00	$145.00
Purchase #6	$228.64	9.636%	$250.6718	$250.67	$250.65	$250.70
Purchase #7	$93.69	12.683%	$105.5727	$105.57	$105.55	$105.60
7 purchase totals =	$1,022.36		$1,117.0996	$1,117.10	$1,117.05	$1,117.10