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	$242.41	10.695%	$268.3357	$268.34	$268.35	$268.30
Purchase #2	$108.87	4.113%	$113.3478	$113.35	$113.35	$113.30
Purchase #3	$146.78	7.872%	$158.3345	$158.33	$158.35	$158.30
Purchase #4	$24.45	3.354%	$25.2701	$25.27	$25.25	$25.30
Purchase #5	$72.52	9.636%	$79.508	$79.51	$79.50	$79.50
Purchase #6	$32.27	11.215%	$35.8891	$35.89	$35.90	$35.90
Purchase #7	$177.94	5.815%	$188.2872	$188.29	$188.30	$188.30
7 purchase totals =	$805.24		$868.9724	$868.98	$869.00	$868.90