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	$48.94	11.764%	$54.6973	$54.70	$54.70	$54.70
Purchase #2	$98.54	10.828%	$109.2099	$109.21	$109.20	$109.20
Purchase #3	$211.69	6.697%	$225.8669	$225.87	$225.85	$225.90
Purchase #4	$89.48	6.520%	$95.3141	$95.31	$95.30	$95.30
Purchase #5	$13.84	8.270%	$14.9846	$14.98	$15.00	$15.00
Purchase #6	$157.78	4.642%	$165.1041	$165.10	$165.10	$165.10
Purchase #7	$67.87	6.740%	$72.4444	$72.44	$72.45	$72.40
7 purchase totals =	$688.14		$737.6213	$737.61	$737.60	$737.60