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	$178.35	7.125%	$191.0574	$191.06	$191.05	$191.10
Purchase #2	$87.43	5.263%	$92.0314	$92.03	$92.05	$92.00
Purchase #3	$16.83	12.312%	$18.9021	$18.90	$18.90	$18.90
Purchase #4	$32.83	11.170%	$36.4971	$36.50	$36.50	$36.50
Purchase #5	$99.79	9.824%	$109.5934	$109.59	$109.60	$109.60
Purchase #6	$233.78	3.379%	$241.6794	$241.68	$241.70	$241.70
Purchase #7	$225.72	11.342%	$251.3212	$251.32	$251.30	$251.30
7 purchase totals =	$874.73		$941.0820	$941.08	$941.10	$941.10