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	$106.29	5.206%	$111.8235	$111.82	$111.80	$111.80
Purchase #2	$103.26	5.563%	$109.0044	$109.00	$109.00	$109.00
Purchase #3	$246.80	6.282%	$262.304	$262.30	$262.30	$262.30
Purchase #4	$27.78	12.172%	$31.1614	$31.16	$31.15	$31.20
Purchase #5	$37.60	3.817%	$39.0352	$39.04	$39.05	$39.00
Purchase #6	$26.60	9.613%	$29.1571	$29.16	$29.15	$29.20
Purchase #7	$169.45	5.393%	$178.5884	$178.59	$178.60	$178.60
7 purchase totals =	$717.78		$761.0740	$761.07	$761.05	$761.10