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	$240.86	10.807%	$266.8897	$266.89	$266.90	$266.90
Purchase #2	$60.61	7.123%	$64.9273	$64.93	$64.95	$64.90
Purchase #3	$53.97	5.196%	$56.7743	$56.77	$56.75	$56.80
Purchase #4	$235.28	3.141%	$242.6701	$242.67	$242.65	$242.70
Purchase #5	$149.78	12.631%	$168.6987	$168.70	$168.70	$168.70
Purchase #6	$104.84	6.519%	$111.6745	$111.67	$111.65	$111.70
Purchase #7	$146.97	5.266%	$154.7094	$154.71	$154.70	$154.70
7 purchase totals =	$992.31		$1,066.3440	$1,066.34	$1,066.30	$1,066.40