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	$148.45	13.481%	$168.4625	$168.46	$168.45	$168.50
Purchase #2	$31.37	10.470%	$34.6544	$34.65	$34.65	$34.70
Purchase #3	$70.66	10.481%	$78.0659	$78.07	$78.05	$78.10
Purchase #4	$135.36	13.684%	$153.8827	$153.88	$153.90	$153.90
Purchase #5	$244.77	3.651%	$253.7066	$253.71	$253.70	$253.70
Purchase #6	$231.97	5.563%	$244.8745	$244.87	$244.85	$244.90
Purchase #7	$245.98	6.844%	$262.8149	$262.81	$262.80	$262.80
7 purchase totals =	$1,108.56		$1,196.4615	$1,196.45	$1,196.40	$1,196.60