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	$127.44	11.451%	$142.0332	$142.03	$142.05	$142.00
Purchase #2	$92.33	7.723%	$99.4606	$99.46	$99.45	$99.50
Purchase #3	$41.87	3.362%	$43.2777	$43.28	$43.30	$43.30
Purchase #4	$21.60	12.619%	$24.3257	$24.33	$24.35	$24.30
Purchase #5	$163.67	3.243%	$168.9778	$168.98	$169.00	$169.00
Purchase #6	$164.37	10.621%	$181.8277	$181.83	$181.85	$181.80
Purchase #7	$191.44	8.779%	$208.2465	$208.25	$208.25	$208.20
7 purchase totals =	$802.72		$868.1492	$868.16	$868.25	$868.10