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	$41.75	5.284%	$43.9561	$43.96	$43.95	$44.00
Purchase #2	$174.74	12.233%	$196.1159	$196.12	$196.10	$196.10
Purchase #3	$82.53	5.159%	$86.7877	$86.79	$86.80	$86.80
Purchase #4	$100.45	8.328%	$108.8155	$108.82	$108.80	$108.80
Purchase #5	$170.77	10.131%	$188.0707	$188.07	$188.05	$188.10
Purchase #6	$123.76	7.325%	$132.8254	$132.83	$132.85	$132.80
Purchase #7	$50.33	13.399%	$57.0737	$57.07	$57.05	$57.10
7 purchase totals =	$744.33		$813.6450	$813.66	$813.60	$813.70