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	$247.75	11.407%	$276.0108	$276.01	$276.00	$276.00
Purchase #2	$69.31	10.397%	$76.5162	$76.52	$76.50	$76.50
Purchase #3	$225.98	4.378%	$235.8734	$235.87	$235.85	$235.90
Purchase #4	$37.30	13.551%	$42.3545	$42.35	$42.35	$42.40
Purchase #5	$79.79	11.851%	$89.2459	$89.25	$89.25	$89.20
Purchase #6	$218.83	10.560%	$241.9384	$241.94	$241.95	$241.90
Purchase #7	$140.48	12.628%	$158.2198	$158.22	$158.20	$158.20
7 purchase totals =	$1,019.44		$1,120.1590	$1,120.16	$1,120.10	$1,120.10