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	$160.37	4.540%	$167.6508	$167.65	$167.65	$167.70
Purchase #2	$135.65	3.295%	$140.1197	$140.12	$140.10	$140.10
Purchase #3	$91.69	13.733%	$104.2818	$104.28	$104.30	$104.30
Purchase #4	$107.95	9.591%	$118.3035	$118.30	$118.30	$118.30
Purchase #5	$33.96	13.714%	$38.6173	$38.62	$38.60	$38.60
Purchase #6	$175.73	11.781%	$196.4328	$196.43	$196.45	$196.40
Purchase #7	$187.63	11.649%	$209.487	$209.49	$209.50	$209.50
7 purchase totals =	$892.98		$974.8929	$974.89	$974.90	$974.90