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	$23.33	4.273%	$24.3269	$24.33	$24.35	$24.30
Purchase #2	$228.27	9.741%	$250.5058	$250.51	$250.50	$250.50
Purchase #3	$235.76	11.673%	$263.2803	$263.28	$263.30	$263.30
Purchase #4	$92.72	13.663%	$105.3883	$105.39	$105.40	$105.40
Purchase #5	$109.57	12.108%	$122.8367	$122.84	$122.85	$122.80
Purchase #6	$19.67	11.339%	$21.9004	$21.90	$21.90	$21.90
Purchase #7	$244.30	4.675%	$255.721	$255.72	$255.70	$255.70
7 purchase totals =	$953.62		$1,043.9594	$1,043.97	$1,044.00	$1,043.90