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	$56.79	4.380%	$59.2774	$59.28	$59.30	$59.30
Purchase #2	$199.90	4.782%	$209.4592	$209.46	$209.45	$209.50
Purchase #3	$6.81	4.517%	$7.1176	$7.12	$7.10	$7.10
Purchase #4	$44.60	6.395%	$47.4522	$47.45	$47.45	$47.50
Purchase #5	$124.55	3.721%	$129.1845	$129.18	$129.20	$129.20
Purchase #6	$152.42	10.528%	$168.4668	$168.47	$168.45	$168.50
Purchase #7	$15.38	11.593%	$17.163	$17.16	$17.15	$17.20
7 purchase totals =	$600.45		$638.1207	$638.12	$638.10	$638.30