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	$242.60	11.214%	$269.8052	$269.81	$269.80	$269.80
Purchase #2	$73.68	5.653%	$77.8451	$77.85	$77.85	$77.80
Purchase #3	$152.94	3.625%	$158.4841	$158.48	$158.50	$158.50
Purchase #4	$35.83	6.277%	$38.079	$38.08	$38.10	$38.10
Purchase #5	$249.34	13.428%	$282.8214	$282.82	$282.80	$282.80
Purchase #6	$187.77	3.509%	$194.3588	$194.36	$194.35	$194.40
Purchase #7	$39.82	7.509%	$42.8101	$42.81	$42.80	$42.80
7 purchase totals =	$981.98		$1,064.2037	$1,064.21	$1,064.20	$1,064.20