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	$240.87	5.663%	$254.5105	$254.51	$254.50	$254.50
Purchase #2	$100.83	6.179%	$107.0603	$107.06	$107.05	$107.10
Purchase #3	$190.45	5.165%	$200.2867	$200.29	$200.30	$200.30
Purchase #4	$122.63	11.619%	$136.8784	$136.88	$136.90	$136.90
Purchase #5	$19.85	13.785%	$22.5863	$22.59	$22.60	$22.60
Purchase #6	$49.70	10.404%	$54.8708	$54.87	$54.85	$54.90
Purchase #7	$167.53	4.571%	$175.1878	$175.19	$175.20	$175.20
7 purchase totals =	$891.86		$951.3808	$951.39	$951.40	$951.50