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	$157.79	11.319%	$175.6503	$175.65	$175.65	$175.70
Purchase #2	$250.64	3.693%	$259.8961	$259.90	$259.90	$259.90
Purchase #3	$183.28	13.734%	$208.4517	$208.45	$208.45	$208.50
Purchase #4	$69.67	4.214%	$72.6059	$72.61	$72.60	$72.60
Purchase #5	$51.50	5.548%	$54.3572	$54.36	$54.35	$54.40
Purchase #6	$162.65	11.606%	$181.5272	$181.53	$181.55	$181.50
Purchase #7	$11.58	10.646%	$12.8128	$12.81	$12.80	$12.80
7 purchase totals =	$887.11		$965.3012	$965.31	$965.30	$965.40