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	$204.34	9.110%	$222.9554	$222.96	$222.95	$223.00
Purchase #2	$41.52	12.670%	$46.7806	$46.78	$46.80	$46.80
Purchase #3	$45.83	4.332%	$47.8154	$47.82	$47.80	$47.80
Purchase #4	$47.89	5.590%	$50.5671	$50.57	$50.55	$50.60
Purchase #5	$233.41	8.766%	$253.8707	$253.87	$253.85	$253.90
Purchase #6	$42.66	3.848%	$44.3016	$44.30	$44.30	$44.30
Purchase #7	$225.37	7.388%	$242.0203	$242.02	$242.00	$242.00
7 purchase totals =	$841.02		$908.3111	$908.32	$908.25	$908.40