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	$44.84	4.331%	$46.782	$46.78	$46.80	$46.80
Purchase #2	$136.71	10.241%	$150.7105	$150.71	$150.70	$150.70
Purchase #3	$62.43	4.227%	$65.0689	$65.07	$65.05	$65.10
Purchase #4	$248.30	10.704%	$274.878	$274.88	$274.90	$274.90
Purchase #5	$163.63	9.158%	$178.6152	$178.62	$178.60	$178.60
Purchase #6	$144.69	7.330%	$155.2958	$155.30	$155.30	$155.30
Purchase #7	$218.28	4.405%	$227.8952	$227.90	$227.90	$227.90
7 purchase totals =	$1,018.88		$1,099.2456	$1,099.26	$1,099.25	$1,099.30