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	$43.29	5.447%	$45.648	$45.65	$45.65	$45.60
Purchase #2	$165.36	8.819%	$179.9431	$179.94	$179.95	$179.90
Purchase #3	$203.97	3.685%	$211.4863	$211.49	$211.50	$211.50
Purchase #4	$70.27	3.490%	$72.7224	$72.72	$72.70	$72.70
Purchase #5	$138.30	12.691%	$155.8517	$155.85	$155.85	$155.90
Purchase #6	$75.92	9.240%	$82.935	$82.94	$82.95	$82.90
Purchase #7	$214.40	13.105%	$242.4971	$242.50	$242.50	$242.50
7 purchase totals =	$911.51		$991.0836	$991.09	$991.10	$991.00