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	$182.51	7.610%	$196.399	$196.40	$196.40	$196.40
Purchase #2	$237.91	7.151%	$254.9229	$254.92	$254.90	$254.90
Purchase #3	$129.77	12.403%	$145.8654	$145.87	$145.85	$145.90
Purchase #4	$100.41	13.639%	$114.1049	$114.10	$114.10	$114.10
Purchase #5	$138.56	10.618%	$153.2723	$153.27	$153.25	$153.30
Purchase #6	$189.48	5.105%	$199.153	$199.15	$199.15	$199.20
Purchase #7	$163.26	9.534%	$178.8252	$178.83	$178.85	$178.80
7 purchase totals =	$1,141.90		$1,242.5427	$1,242.54	$1,242.50	$1,242.60