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	$203.37	4.704%	$212.9365	$212.94	$212.95	$212.90
Purchase #2	$125.81	12.380%	$141.3853	$141.39	$141.40	$141.40
Purchase #3	$153.38	4.735%	$160.6425	$160.64	$160.65	$160.60
Purchase #4	$72.59	13.262%	$82.2169	$82.22	$82.20	$82.20
Purchase #5	$43.72	10.549%	$48.332	$48.33	$48.35	$48.30
Purchase #6	$94.53	6.408%	$100.5875	$100.59	$100.60	$100.60
Purchase #7	$158.38	3.262%	$163.5464	$163.55	$163.55	$163.50
7 purchase totals =	$851.78		$909.6471	$909.66	$909.70	$909.50