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	$89.60	7.283%	$96.1256	$96.13	$96.15	$96.10
Purchase #2	$75.50	9.678%	$82.8069	$82.81	$82.80	$82.80
Purchase #3	$141.26	11.560%	$157.5897	$157.59	$157.60	$157.60
Purchase #4	$68.28	13.821%	$77.717	$77.72	$77.70	$77.70
Purchase #5	$191.47	4.491%	$200.0689	$200.07	$200.05	$200.10
Purchase #6	$152.53	6.546%	$162.5146	$162.51	$162.50	$162.50
Purchase #7	$183.56	11.152%	$204.0306	$204.03	$204.05	$204.00
7 purchase totals =	$902.20		$980.8533	$980.86	$980.85	$980.80