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	$142.47	8.181%	$154.1255	$154.13	$154.15	$154.10
Purchase #2	$87.52	11.215%	$97.3354	$97.34	$97.35	$97.30
Purchase #3	$74.56	5.810%	$78.8919	$78.89	$78.90	$78.90
Purchase #4	$39.38	7.451%	$42.3142	$42.31	$42.30	$42.30
Purchase #5	$208.29	5.581%	$219.9147	$219.91	$219.90	$219.90
Purchase #6	$75.50	8.757%	$82.1115	$82.11	$82.10	$82.10
Purchase #7	$177.55	6.858%	$189.7264	$189.73	$189.75	$189.70
7 purchase totals =	$805.27		$864.4196	$864.42	$864.45	$864.30