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	$107.46	4.641%	$112.4472	$112.45	$112.45	$112.40
Purchase #2	$223.55	7.729%	$240.8282	$240.83	$240.85	$240.80
Purchase #3	$50.30	8.489%	$54.57	$54.57	$54.55	$54.60
Purchase #4	$63.77	6.104%	$67.6625	$67.66	$67.65	$67.70
Purchase #5	$233.62	9.373%	$255.5172	$255.52	$255.50	$255.50
Purchase #6	$154.34	3.224%	$159.3159	$159.32	$159.30	$159.30
Purchase #7	$65.31	6.104%	$69.2965	$69.30	$69.30	$69.30
7 purchase totals =	$898.35		$959.6375	$959.65	$959.60	$959.60