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	$173.26	13.355%	$196.3989	$196.40	$196.40	$196.40
Purchase #2	$16.96	7.436%	$18.2211	$18.22	$18.20	$18.20
Purchase #3	$185.26	11.538%	$206.6353	$206.64	$206.65	$206.60
Purchase #4	$52.81	4.439%	$55.1542	$55.15	$55.15	$55.20
Purchase #5	$68.45	10.352%	$75.5359	$75.54	$75.55	$75.50
Purchase #6	$157.98	5.444%	$166.5804	$166.58	$166.60	$166.60
Purchase #7	$77.57	6.453%	$82.5756	$82.58	$82.60	$82.60
7 purchase totals =	$732.29		$801.1014	$801.11	$801.15	$801.10