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	$203.49	11.300%	$226.4844	$226.48	$226.50	$226.50
Purchase #2	$31.89	3.725%	$33.0779	$33.08	$33.10	$33.10
Purchase #3	$200.86	9.413%	$219.767	$219.77	$219.75	$219.80
Purchase #4	$151.63	7.150%	$162.4715	$162.47	$162.45	$162.50
Purchase #5	$49.81	6.116%	$52.8564	$52.86	$52.85	$52.90
Purchase #6	$27.60	5.306%	$29.0645	$29.06	$29.05	$29.10
Purchase #7	$98.81	13.863%	$112.508	$112.51	$112.50	$112.50
7 purchase totals =	$764.09		$836.2297	$836.23	$836.20	$836.40