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	$104.39	3.709%	$108.2618	$108.26	$108.25	$108.30
Purchase #2	$69.65	12.628%	$78.4454	$78.45	$78.45	$78.40
Purchase #3	$243.40	8.426%	$263.9089	$263.91	$263.90	$263.90
Purchase #4	$87.33	3.169%	$90.0975	$90.10	$90.10	$90.10
Purchase #5	$221.51	12.833%	$249.9364	$249.94	$249.95	$249.90
Purchase #6	$197.35	8.809%	$214.7346	$214.73	$214.75	$214.70
Purchase #7	$123.40	6.397%	$131.2939	$131.29	$131.30	$131.30
7 purchase totals =	$1,047.03		$1,136.6785	$1,136.68	$1,136.70	$1,136.60