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	$82.39	12.693%	$92.8478	$92.85	$92.85	$92.80
Purchase #2	$45.50	11.530%	$50.7462	$50.75	$50.75	$50.70
Purchase #3	$130.81	6.109%	$138.8012	$138.80	$138.80	$138.80
Purchase #4	$104.30	13.573%	$118.4566	$118.46	$118.45	$118.50
Purchase #5	$174.97	12.405%	$196.675	$196.68	$196.70	$196.70
Purchase #6	$149.73	12.570%	$168.5511	$168.55	$168.55	$168.60
Purchase #7	$237.30	3.493%	$245.5889	$245.59	$245.60	$245.60
7 purchase totals =	$925.00		$1,011.6668	$1,011.68	$1,011.70	$1,011.70