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	$41.38	9.670%	$45.3814	$45.38	$45.40	$45.40
Purchase #2	$51.27	6.579%	$54.6431	$54.64	$54.65	$54.60
Purchase #3	$249.66	10.394%	$275.6097	$275.61	$275.60	$275.60
Purchase #4	$88.78	7.405%	$95.3542	$95.35	$95.35	$95.40
Purchase #5	$111.93	8.462%	$121.4015	$121.40	$121.40	$121.40
Purchase #6	$181.31	9.419%	$198.3876	$198.39	$198.40	$198.40
Purchase #7	$179.75	13.825%	$204.6004	$204.60	$204.60	$204.60
7 purchase totals =	$904.08		$995.3779	$995.37	$995.40	$995.40