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	$158.46	9.311%	$173.2142	$173.21	$173.20	$173.20
Purchase #2	$168.80	4.541%	$176.4652	$176.47	$176.45	$176.50
Purchase #3	$132.37	9.548%	$145.0087	$145.01	$145.00	$145.00
Purchase #4	$104.84	6.323%	$111.469	$111.47	$111.45	$111.50
Purchase #5	$223.26	7.622%	$240.2769	$240.28	$240.30	$240.30
Purchase #6	$212.55	3.460%	$219.9042	$219.90	$219.90	$219.90
Purchase #7	$157.34	11.152%	$174.8866	$174.89	$174.90	$174.90
7 purchase totals =	$1,157.62		$1,241.2248	$1,241.23	$1,241.20	$1,241.30