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	$183.81	12.467%	$206.7256	$206.73	$206.75	$206.70
Purchase #2	$24.73	3.445%	$25.5819	$25.58	$25.60	$25.60
Purchase #3	$149.33	11.577%	$166.6179	$166.62	$166.60	$166.60
Purchase #4	$67.59	12.761%	$76.2152	$76.22	$76.20	$76.20
Purchase #5	$98.96	10.620%	$109.4696	$109.47	$109.45	$109.50
Purchase #6	$174.63	12.325%	$196.1531	$196.15	$196.15	$196.20
Purchase #7	$161.36	10.816%	$178.8127	$178.81	$178.80	$178.80
7 purchase totals =	$860.41		$959.5760	$959.58	$959.55	$959.60