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	$86.40	9.275%	$94.4136	$94.41	$94.40	$94.40
Purchase #2	$107.50	3.288%	$111.0346	$111.03	$111.05	$111.00
Purchase #3	$59.54	4.762%	$62.3753	$62.38	$62.40	$62.40
Purchase #4	$184.30	4.454%	$192.5087	$192.51	$192.50	$192.50
Purchase #5	$141.47	7.627%	$152.2599	$152.26	$152.25	$152.30
Purchase #6	$102.62	5.377%	$108.1379	$108.14	$108.15	$108.10
Purchase #7	$61.49	13.690%	$69.908	$69.91	$69.90	$69.90
7 purchase totals =	$743.32		$790.6380	$790.64	$790.65	$790.60