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	$184.50	4.387%	$192.594	$192.59	$192.60	$192.60
Purchase #2	$198.92	6.334%	$211.5196	$211.52	$211.50	$211.50
Purchase #3	$78.76	8.305%	$85.301	$85.30	$85.30	$85.30
Purchase #4	$230.37	3.320%	$238.0183	$238.02	$238.00	$238.00
Purchase #5	$26.77	7.725%	$28.838	$28.84	$28.85	$28.80
Purchase #6	$171.30	5.680%	$181.0298	$181.03	$181.05	$181.00
Purchase #7	$9.73	8.823%	$10.5885	$10.59	$10.60	$10.60
7 purchase totals =	$900.35		$947.8892	$947.89	$947.90	$947.80