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	$38.37	5.404%	$40.4435	$40.44	$40.45	$40.40
Purchase #2	$82.82	11.841%	$92.6267	$92.63	$92.65	$92.60
Purchase #3	$246.70	13.788%	$280.715	$280.72	$280.70	$280.70
Purchase #4	$65.36	5.174%	$68.7417	$68.74	$68.75	$68.70
Purchase #5	$59.66	8.180%	$64.5402	$64.54	$64.55	$64.50
Purchase #6	$63.50	4.370%	$66.275	$66.28	$66.30	$66.30
Purchase #7	$10.72	3.593%	$11.1052	$11.11	$11.10	$11.10
7 purchase totals =	$567.13		$624.4473	$624.46	$624.50	$624.30