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	$119.45	3.205%	$123.2784	$123.28	$123.30	$123.30
Purchase #2	$39.28	3.781%	$40.7652	$40.77	$40.75	$40.80
Purchase #3	$14.77	9.867%	$16.2274	$16.23	$16.25	$16.20
Purchase #4	$179.75	11.606%	$200.6118	$200.61	$200.60	$200.60
Purchase #5	$66.74	8.711%	$72.5537	$72.55	$72.55	$72.60
Purchase #6	$240.51	8.846%	$261.7855	$261.79	$261.80	$261.80
Purchase #7	$206.94	11.408%	$230.5477	$230.55	$230.55	$230.50
7 purchase totals =	$867.44		$945.7697	$945.78	$945.80	$945.80