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	$69.71	7.420%	$74.8825	$74.88	$74.90	$74.90
Purchase #2	$74.40	10.850%	$82.4724	$82.47	$82.45	$82.50
Purchase #3	$218.60	10.708%	$242.0077	$242.01	$242.00	$242.00
Purchase #4	$115.63	10.397%	$127.6521	$127.65	$127.65	$127.70
Purchase #5	$118.98	10.508%	$131.4824	$131.48	$131.50	$131.50
Purchase #6	$234.73	13.216%	$265.7519	$265.75	$265.75	$265.80
Purchase #7	$38.32	10.327%	$42.2773	$42.28	$42.30	$42.30
7 purchase totals =	$870.37		$966.5263	$966.52	$966.55	$966.70