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	$64.28	5.403%	$67.753	$67.75	$67.75	$67.80
Purchase #2	$83.59	9.814%	$91.7935	$91.79	$91.80	$91.80
Purchase #3	$199.51	10.277%	$220.0136	$220.01	$220.00	$220.00
Purchase #4	$70.52	11.810%	$78.8484	$78.85	$78.85	$78.80
Purchase #5	$56.25	10.152%	$61.9605	$61.96	$61.95	$62.00
Purchase #6	$78.87	5.435%	$83.1566	$83.16	$83.15	$83.20
Purchase #7	$25.66	13.153%	$29.0351	$29.04	$29.05	$29.00
7 purchase totals =	$578.68		$632.5607	$632.56	$632.55	$632.60