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	$46.61	4.257%	$48.5942	$48.59	$48.60	$48.60
Purchase #2	$79.42	12.650%	$89.4666	$89.47	$89.45	$89.50
Purchase #3	$125.89	5.408%	$132.6981	$132.70	$132.70	$132.70
Purchase #4	$180.43	13.351%	$204.5192	$204.52	$204.50	$204.50
Purchase #5	$55.44	4.424%	$57.8927	$57.89	$57.90	$57.90
Purchase #6	$30.32	3.500%	$31.3812	$31.38	$31.40	$31.40
Purchase #7	$245.53	6.760%	$262.1278	$262.13	$262.15	$262.10
7 purchase totals =	$763.64		$826.6798	$826.68	$826.70	$826.70