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	$40.77	11.564%	$45.4846	$45.48	$45.50	$45.50
Purchase #2	$242.50	11.112%	$269.4466	$269.45	$269.45	$269.40
Purchase #3	$13.51	6.167%	$14.3432	$14.34	$14.35	$14.30
Purchase #4	$43.72	5.286%	$46.031	$46.03	$46.05	$46.00
Purchase #5	$109.28	12.831%	$123.3017	$123.30	$123.30	$123.30
Purchase #6	$200.91	6.269%	$213.505	$213.51	$213.50	$213.50
Purchase #7	$144.79	5.806%	$153.1965	$153.20	$153.20	$153.20
7 purchase totals =	$795.48		$865.3086	$865.31	$865.35	$865.20