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	$15.36	3.666%	$15.9231	$15.92	$15.90	$15.90
Purchase #2	$24.85	13.328%	$28.162	$28.16	$28.15	$28.20
Purchase #3	$160.29	11.331%	$178.4525	$178.45	$178.45	$178.50
Purchase #4	$223.29	5.110%	$234.7001	$234.70	$234.70	$234.70
Purchase #5	$41.94	9.127%	$45.7679	$45.77	$45.75	$45.80
Purchase #6	$220.75	9.328%	$241.3416	$241.34	$241.35	$241.30
Purchase #7	$189.88	3.366%	$196.2714	$196.27	$196.25	$196.30
7 purchase totals =	$876.36		$940.6186	$940.61	$940.55	$940.70