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	$34.97	6.628%	$37.2878	$37.29	$37.30	$37.30
Purchase #2	$86.73	12.405%	$97.4889	$97.49	$97.50	$97.50
Purchase #3	$55.42	5.395%	$58.4099	$58.41	$58.40	$58.40
Purchase #4	$68.38	11.766%	$76.4256	$76.43	$76.45	$76.40
Purchase #5	$9.57	10.591%	$10.5836	$10.58	$10.60	$10.60
Purchase #6	$69.26	13.437%	$78.5665	$78.57	$78.55	$78.60
Purchase #7	$38.29	13.686%	$43.5304	$43.53	$43.55	$43.50
7 purchase totals =	$362.62		$402.2927	$402.30	$402.35	$402.30