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	$96.95	8.386%	$105.0802	$105.08	$105.10	$105.10
Purchase #2	$125.82	9.151%	$137.3338	$137.33	$137.35	$137.30
Purchase #3	$152.95	10.103%	$168.4025	$168.40	$168.40	$168.40
Purchase #4	$128.60	9.694%	$141.0665	$141.07	$141.05	$141.10
Purchase #5	$138.82	10.174%	$152.9435	$152.94	$152.95	$152.90
Purchase #6	$205.61	9.197%	$224.52	$224.52	$224.50	$224.50
Purchase #7	$74.85	5.191%	$78.7355	$78.74	$78.75	$78.70
7 purchase totals =	$923.60		$1,008.0820	$1,008.08	$1,008.10	$1,008.00