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	$73.66	6.530%	$78.47	$78.47	$78.45	$78.50
Purchase #2	$97.64	6.212%	$103.7054	$103.71	$103.70	$103.70
Purchase #3	$121.77	10.328%	$134.3464	$134.35	$134.35	$134.30
Purchase #4	$214.77	5.702%	$227.0162	$227.02	$227.00	$227.00
Purchase #5	$41.64	9.834%	$45.7349	$45.73	$45.75	$45.70
Purchase #6	$13.42	7.372%	$14.4093	$14.41	$14.40	$14.40
Purchase #7	$124.92	12.539%	$140.5837	$140.58	$140.60	$140.60
7 purchase totals =	$687.82		$744.2659	$744.27	$744.25	$744.20