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	$218.64	4.114%	$227.6348	$227.63	$227.65	$227.60
Purchase #2	$216.68	4.243%	$225.8737	$225.87	$225.85	$225.90
Purchase #3	$154.43	5.511%	$162.9406	$162.94	$162.95	$162.90
Purchase #4	$92.97	9.564%	$101.8617	$101.86	$101.85	$101.90
Purchase #5	$238.65	6.592%	$254.3818	$254.38	$254.40	$254.40
Purchase #6	$45.25	11.210%	$50.3225	$50.32	$50.30	$50.30
Purchase #7	$95.44	13.341%	$108.1727	$108.17	$108.15	$108.20
7 purchase totals =	$1,062.06		$1,131.1878	$1,131.17	$1,131.15	$1,131.20