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	$245.77	11.514%	$274.068	$274.07	$274.05	$274.10
Purchase #2	$149.92	11.333%	$166.9104	$166.91	$166.90	$166.90
Purchase #3	$146.68	5.403%	$154.6051	$154.61	$154.60	$154.60
Purchase #4	$17.88	5.526%	$18.868	$18.87	$18.85	$18.90
Purchase #5	$138.82	5.546%	$146.519	$146.52	$146.50	$146.50
Purchase #6	$105.94	7.460%	$113.8431	$113.84	$113.85	$113.80
Purchase #7	$168.75	10.151%	$185.8798	$185.88	$185.90	$185.90
7 purchase totals =	$973.76		$1,060.6934	$1,060.70	$1,060.65	$1,060.70