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	$132.63	11.281%	$147.592	$147.59	$147.60	$147.60
Purchase #2	$220.86	5.804%	$233.6787	$233.68	$233.70	$233.70
Purchase #3	$16.45	8.614%	$17.867	$17.87	$17.85	$17.90
Purchase #4	$138.98	12.289%	$156.0593	$156.06	$156.05	$156.10
Purchase #5	$63.60	13.277%	$72.0442	$72.04	$72.05	$72.00
Purchase #6	$31.72	10.539%	$35.063	$35.06	$35.05	$35.10
Purchase #7	$90.95	9.543%	$99.6294	$99.63	$99.65	$99.60
7 purchase totals =	$695.19		$761.9336	$761.93	$761.95	$762.00