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	$34.59	11.383%	$38.5274	$38.53	$38.55	$38.50
Purchase #2	$210.32	11.286%	$234.0567	$234.06	$234.05	$234.10
Purchase #3	$21.34	5.693%	$22.5549	$22.55	$22.55	$22.60
Purchase #4	$92.39	8.262%	$100.0233	$100.02	$100.00	$100.00
Purchase #5	$124.76	11.482%	$139.0849	$139.08	$139.10	$139.10
Purchase #6	$170.26	8.271%	$184.3422	$184.34	$184.35	$184.30
Purchase #7	$156.52	5.324%	$164.8531	$164.85	$164.85	$164.90
7 purchase totals =	$810.18		$883.4425	$883.43	$883.45	$883.50