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	$95.95	12.468%	$107.913	$107.91	$107.90	$107.90
Purchase #2	$241.46	9.472%	$264.3311	$264.33	$264.35	$264.30
Purchase #3	$39.61	7.110%	$42.4263	$42.43	$42.45	$42.40
Purchase #4	$170.86	4.136%	$177.9268	$177.93	$177.95	$177.90
Purchase #5	$237.25	4.314%	$247.485	$247.49	$247.50	$247.50
Purchase #6	$89.92	12.125%	$100.8228	$100.82	$100.80	$100.80
Purchase #7	$167.47	3.633%	$173.5542	$173.55	$173.55	$173.60
7 purchase totals =	$1,042.52		$1,114.4592	$1,114.46	$1,114.50	$1,114.40