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	$57.71	13.174%	$65.3127	$65.31	$65.30	$65.30
Purchase #2	$228.89	5.599%	$241.7056	$241.71	$241.70	$241.70
Purchase #3	$72.99	13.872%	$83.1152	$83.12	$83.10	$83.10
Purchase #4	$78.83	8.602%	$85.611	$85.61	$85.60	$85.60
Purchase #5	$140.58	6.792%	$150.1282	$150.13	$150.15	$150.10
Purchase #6	$187.32	5.722%	$198.0385	$198.04	$198.05	$198.00
Purchase #7	$76.54	6.276%	$81.3437	$81.34	$81.35	$81.30
7 purchase totals =	$842.86		$905.2549	$905.26	$905.25	$905.10