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	$69.25	13.472%	$78.5794	$78.58	$78.60	$78.60
Purchase #2	$160.90	3.388%	$166.3513	$166.35	$166.35	$166.40
Purchase #3	$150.31	11.231%	$167.1913	$167.19	$167.20	$167.20
Purchase #4	$121.40	4.526%	$126.8946	$126.89	$126.90	$126.90
Purchase #5	$37.28	13.152%	$42.1831	$42.18	$42.20	$42.20
Purchase #6	$154.40	12.812%	$174.1817	$174.18	$174.20	$174.20
Purchase #7	$91.50	6.248%	$97.2169	$97.22	$97.20	$97.20
7 purchase totals =	$785.04		$852.5983	$852.59	$852.65	$852.70