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	$223.37	3.339%	$230.8283	$230.83	$230.85	$230.80
Purchase #2	$164.65	9.594%	$180.4465	$180.45	$180.45	$180.40
Purchase #3	$157.36	4.795%	$164.9054	$164.91	$164.90	$164.90
Purchase #4	$226.98	7.508%	$244.0217	$244.02	$244.00	$244.00
Purchase #5	$164.30	8.613%	$178.4512	$178.45	$178.45	$178.50
Purchase #6	$45.46	7.747%	$48.9818	$48.98	$49.00	$49.00
Purchase #7	$46.37	11.765%	$51.8254	$51.83	$51.85	$51.80
7 purchase totals =	$1,028.49		$1,099.4603	$1,099.47	$1,099.50	$1,099.40