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	$150.52	11.503%	$167.8343	$167.83	$167.85	$167.80
Purchase #2	$139.30	10.850%	$154.4141	$154.41	$154.40	$154.40
Purchase #3	$128.45	12.546%	$144.5653	$144.57	$144.55	$144.60
Purchase #4	$57.94	3.183%	$59.7842	$59.78	$59.80	$59.80
Purchase #5	$89.50	12.321%	$100.5273	$100.53	$100.55	$100.50
Purchase #6	$210.86	11.328%	$234.7462	$234.75	$234.75	$234.70
Purchase #7	$129.85	12.314%	$145.8397	$145.84	$145.85	$145.80
7 purchase totals =	$906.42		$1,007.7111	$1,007.71	$1,007.75	$1,007.60