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	$151.59	13.437%	$171.9591	$171.96	$171.95	$172.00
Purchase #2	$157.70	5.817%	$166.8734	$166.87	$166.85	$166.90
Purchase #3	$244.62	7.393%	$262.7048	$262.70	$262.70	$262.70
Purchase #4	$204.50	4.817%	$214.3508	$214.35	$214.35	$214.40
Purchase #5	$174.93	12.282%	$196.4149	$196.41	$196.40	$196.40
Purchase #6	$67.37	13.583%	$76.5209	$76.52	$76.50	$76.50
Purchase #7	$36.56	4.224%	$38.1043	$38.10	$38.10	$38.10
7 purchase totals =	$1,037.27		$1,126.9282	$1,126.91	$1,126.85	$1,127.00