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	$169.59	12.204%	$190.2868	$190.29	$190.30	$190.30
Purchase #2	$219.71	3.299%	$226.9582	$226.96	$226.95	$227.00
Purchase #3	$186.29	4.509%	$194.6898	$194.69	$194.70	$194.70
Purchase #4	$146.68	8.325%	$158.8911	$158.89	$158.90	$158.90
Purchase #5	$46.40	7.797%	$50.0178	$50.02	$50.00	$50.00
Purchase #6	$75.83	12.616%	$85.3967	$85.40	$85.40	$85.40
Purchase #7	$91.84	12.510%	$103.3292	$103.33	$103.35	$103.30
7 purchase totals =	$936.34		$1,009.5696	$1,009.58	$1,009.60	$1,009.60