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	$137.98	11.467%	$153.8022	$153.80	$153.80	$153.80
Purchase #2	$194.79	10.575%	$215.389	$215.39	$215.40	$215.40
Purchase #3	$91.59	3.491%	$94.7874	$94.79	$94.80	$94.80
Purchase #4	$70.49	11.495%	$78.5928	$78.59	$78.60	$78.60
Purchase #5	$98.86	10.215%	$108.9585	$108.96	$108.95	$109.00
Purchase #6	$88.51	3.468%	$91.5795	$91.58	$91.60	$91.60
Purchase #7	$204.69	4.874%	$214.6666	$214.67	$214.65	$214.70
7 purchase totals =	$886.91		$957.7760	$957.78	$957.80	$957.90