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	$153.55	4.579%	$160.5811	$160.58	$160.60	$160.60
Purchase #2	$183.85	3.166%	$189.6707	$189.67	$189.65	$189.70
Purchase #3	$139.40	4.161%	$145.2004	$145.20	$145.20	$145.20
Purchase #4	$186.60	5.550%	$196.9563	$196.96	$196.95	$197.00
Purchase #5	$37.89	6.485%	$40.3472	$40.35	$40.35	$40.30
Purchase #6	$145.72	8.181%	$157.6414	$157.64	$157.65	$157.60
Purchase #7	$53.38	6.618%	$56.9127	$56.91	$56.90	$56.90
7 purchase totals =	$900.39		$947.3098	$947.31	$947.30	$947.30