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	$59.93	12.305%	$67.3044	$67.30	$67.30	$67.30
Purchase #2	$202.31	11.248%	$225.0658	$225.07	$225.05	$225.10
Purchase #3	$213.36	4.319%	$222.575	$222.58	$222.60	$222.60
Purchase #4	$239.83	6.590%	$255.6348	$255.63	$255.65	$255.60
Purchase #5	$18.65	13.370%	$21.1435	$21.14	$21.15	$21.10
Purchase #6	$122.91	11.279%	$136.773	$136.77	$136.75	$136.80
Purchase #7	$127.54	3.744%	$132.3151	$132.32	$132.30	$132.30
7 purchase totals =	$984.53		$1,060.8116	$1,060.81	$1,060.80	$1,060.80