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	$95.89	13.324%	$108.6664	$108.67	$108.65	$108.70
Purchase #2	$86.52	4.800%	$90.673	$90.67	$90.65	$90.70
Purchase #3	$54.28	9.311%	$59.334	$59.33	$59.35	$59.30
Purchase #4	$225.47	4.419%	$235.4335	$235.43	$235.45	$235.40
Purchase #5	$28.56	12.358%	$32.0894	$32.09	$32.10	$32.10
Purchase #6	$195.82	6.631%	$208.8048	$208.80	$208.80	$208.80
Purchase #7	$139.83	6.168%	$148.4547	$148.45	$148.45	$148.50
7 purchase totals =	$826.37		$883.4558	$883.44	$883.45	$883.50