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	$59.37	10.395%	$65.5415	$65.54	$65.55	$65.50
Purchase #2	$167.94	10.424%	$185.4461	$185.45	$185.45	$185.40
Purchase #3	$39.50	5.836%	$41.8052	$41.81	$41.80	$41.80
Purchase #4	$221.82	13.722%	$252.2581	$252.26	$252.25	$252.30
Purchase #5	$133.44	4.468%	$139.4021	$139.40	$139.40	$139.40
Purchase #6	$187.42	11.268%	$208.5385	$208.54	$208.55	$208.50
Purchase #7	$38.34	10.322%	$42.2975	$42.30	$42.30	$42.30
7 purchase totals =	$847.83		$935.2890	$935.30	$935.30	$935.20