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	$41.47	9.754%	$45.515	$45.52	$45.50	$45.50
Purchase #2	$68.90	4.418%	$71.944	$71.94	$71.95	$71.90
Purchase #3	$172.93	3.310%	$178.654	$178.65	$178.65	$178.70
Purchase #4	$136.55	3.366%	$141.1463	$141.15	$141.15	$141.10
Purchase #5	$52.25	10.254%	$57.6077	$57.61	$57.60	$57.60
Purchase #6	$226.63	11.660%	$253.0551	$253.06	$253.05	$253.10
Purchase #7	$129.90	10.306%	$143.2875	$143.29	$143.30	$143.30
7 purchase totals =	$828.63		$891.2096	$891.22	$891.20	$891.20