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	$42.39	9.452%	$46.3967	$46.40	$46.40	$46.40
Purchase #2	$134.72	13.494%	$152.8991	$152.90	$152.90	$152.90
Purchase #3	$34.33	9.153%	$37.4722	$37.47	$37.45	$37.50
Purchase #4	$212.65	4.759%	$222.77	$222.77	$222.75	$222.80
Purchase #5	$196.46	9.356%	$214.8408	$214.84	$214.85	$214.80
Purchase #6	$40.49	10.707%	$44.8253	$44.83	$44.85	$44.80
Purchase #7	$173.38	5.201%	$182.3975	$182.40	$182.40	$182.40
7 purchase totals =	$834.42		$901.6016	$901.61	$901.60	$901.60