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	$160.63	5.802%	$169.9498	$169.95	$169.95	$169.90
Purchase #2	$72.98	8.195%	$78.9607	$78.96	$78.95	$79.00
Purchase #3	$103.45	8.249%	$111.9836	$111.98	$112.00	$112.00
Purchase #4	$102.72	13.344%	$116.427	$116.43	$116.45	$116.40
Purchase #5	$5.31	7.760%	$5.7221	$5.72	$5.70	$5.70
Purchase #6	$247.40	13.798%	$281.5363	$281.54	$281.55	$281.50
Purchase #7	$50.68	6.161%	$53.8024	$53.80	$53.80	$53.80
7 purchase totals =	$743.17		$818.3819	$818.38	$818.40	$818.30