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	$153.33	6.426%	$163.183	$163.18	$163.20	$163.20
Purchase #2	$41.69	3.465%	$43.1346	$43.13	$43.15	$43.10
Purchase #3	$71.78	7.869%	$77.4284	$77.43	$77.45	$77.40
Purchase #4	$29.26	11.431%	$32.6047	$32.60	$32.60	$32.60
Purchase #5	$182.87	7.342%	$196.2963	$196.30	$196.30	$196.30
Purchase #6	$155.62	6.328%	$165.4676	$165.47	$165.45	$165.50
Purchase #7	$99.25	6.641%	$105.8412	$105.84	$105.85	$105.80
7 purchase totals =	$733.80		$783.9558	$783.95	$784.00	$783.90