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	$20.73	10.578%	$22.9228	$22.92	$22.90	$22.90
Purchase #2	$100.88	8.308%	$109.2611	$109.26	$109.25	$109.30
Purchase #3	$95.51	4.545%	$99.8509	$99.85	$99.85	$99.90
Purchase #4	$197.26	11.389%	$219.7259	$219.73	$219.75	$219.70
Purchase #5	$192.45	5.716%	$203.4504	$203.45	$203.45	$203.50
Purchase #6	$172.60	5.358%	$181.8479	$181.85	$181.85	$181.80
Purchase #7	$165.43	12.624%	$186.3139	$186.31	$186.30	$186.30
7 purchase totals =	$944.86		$1,023.3729	$1,023.37	$1,023.35	$1,023.40