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	$242.82	8.573%	$263.637	$263.64	$263.65	$263.60
Purchase #2	$89.99	11.182%	$100.0527	$100.05	$100.05	$100.10
Purchase #3	$172.74	13.739%	$196.4727	$196.47	$196.45	$196.50
Purchase #4	$191.51	9.332%	$209.3817	$209.38	$209.40	$209.40
Purchase #5	$209.28	4.228%	$218.1284	$218.13	$218.15	$218.10
Purchase #6	$85.97	6.162%	$91.2675	$91.27	$91.25	$91.30
Purchase #7	$225.45	8.254%	$244.0586	$244.06	$244.05	$244.10
7 purchase totals =	$1,217.76		$1,322.9986	$1,323.00	$1,323.00	$1,323.10