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	$184.57	13.690%	$209.8376	$209.84	$209.85	$209.80
Purchase #2	$233.94	7.675%	$251.8949	$251.89	$251.90	$251.90
Purchase #3	$18.40	10.303%	$20.2958	$20.30	$20.30	$20.30
Purchase #4	$164.83	13.817%	$187.6046	$187.60	$187.60	$187.60
Purchase #5	$85.47	7.549%	$91.9221	$91.92	$91.90	$91.90
Purchase #6	$134.28	9.826%	$147.4744	$147.47	$147.45	$147.50
Purchase #7	$230.68	4.407%	$240.8461	$240.85	$240.85	$240.80
7 purchase totals =	$1,052.17		$1,149.8755	$1,149.87	$1,149.85	$1,149.80