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	$162.25	6.559%	$172.892	$172.89	$172.90	$172.90
Purchase #2	$158.47	12.242%	$177.8699	$177.87	$177.85	$177.90
Purchase #3	$177.29	8.204%	$191.8349	$191.83	$191.85	$191.80
Purchase #4	$65.31	3.813%	$67.8003	$67.80	$67.80	$67.80
Purchase #5	$245.40	6.562%	$261.5031	$261.50	$261.50	$261.50
Purchase #6	$167.29	12.236%	$187.7596	$187.76	$187.75	$187.80
Purchase #7	$238.60	12.855%	$269.272	$269.27	$269.25	$269.30
7 purchase totals =	$1,214.61		$1,328.9318	$1,328.92	$1,328.90	$1,329.00