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	$150.88	3.435%	$156.0627	$156.06	$156.05	$156.10
Purchase #2	$141.94	9.822%	$155.8813	$155.88	$155.90	$155.90
Purchase #3	$75.35	11.160%	$83.7591	$83.76	$83.75	$83.80
Purchase #4	$69.49	11.678%	$77.605	$77.61	$77.60	$77.60
Purchase #5	$17.28	6.500%	$18.4032	$18.40	$18.40	$18.40
Purchase #6	$74.83	6.734%	$79.8691	$79.87	$79.85	$79.90
Purchase #7	$231.82	13.293%	$262.6358	$262.64	$262.65	$262.60
7 purchase totals =	$761.59		$834.2162	$834.22	$834.20	$834.30