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	$203.88	5.694%	$215.4889	$215.49	$215.50	$215.50
Purchase #2	$221.69	9.117%	$241.9015	$241.90	$241.90	$241.90
Purchase #3	$118.88	3.671%	$123.2441	$123.24	$123.25	$123.20
Purchase #4	$64.66	6.818%	$69.0685	$69.07	$69.05	$69.10
Purchase #5	$20.83	13.477%	$23.6373	$23.64	$23.65	$23.60
Purchase #6	$238.78	4.865%	$250.3966	$250.40	$250.40	$250.40
Purchase #7	$96.89	3.856%	$100.6261	$100.63	$100.65	$100.60
7 purchase totals =	$965.61		$1,024.3630	$1,024.37	$1,024.40	$1,024.30