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	$83.41	11.172%	$92.7286	$92.73	$92.75	$92.70
Purchase #2	$14.78	3.305%	$15.2685	$15.27	$15.25	$15.30
Purchase #3	$20.56	5.672%	$21.7262	$21.73	$21.75	$21.70
Purchase #4	$66.91	5.500%	$70.5901	$70.59	$70.60	$70.60
Purchase #5	$204.51	13.103%	$231.3069	$231.31	$231.30	$231.30
Purchase #6	$185.26	12.773%	$208.9233	$208.92	$208.90	$208.90
Purchase #7	$181.54	13.111%	$205.3417	$205.34	$205.35	$205.30
7 purchase totals =	$756.97		$845.8853	$845.89	$845.90	$845.80