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	$124.41	5.362%	$131.0809	$131.08	$131.10	$131.10
Purchase #2	$103.64	4.759%	$108.5722	$108.57	$108.55	$108.60
Purchase #3	$99.87	11.442%	$111.2971	$111.30	$111.30	$111.30
Purchase #4	$149.51	5.357%	$157.5193	$157.52	$157.50	$157.50
Purchase #5	$166.92	4.169%	$173.8789	$173.88	$173.90	$173.90
Purchase #6	$149.91	5.202%	$157.7083	$157.71	$157.70	$157.70
Purchase #7	$240.87	11.860%	$269.4372	$269.44	$269.45	$269.40
7 purchase totals =	$1,035.13		$1,109.4939	$1,109.50	$1,109.50	$1,109.50