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	5.797%	$36.9972	$37.00	$37.00	$37.00
Purchase #2	$29.27	4.196%	$30.4982	$30.50	$30.50	$30.50
Purchase #3	$35.83	7.816%	$38.6305	$38.63	$38.65	$38.60
Purchase #4	$64.59	11.615%	$72.0921	$72.09	$72.10	$72.10
Purchase #5	$53.60	11.110%	$59.555	$59.56	$59.55	$59.60
Purchase #6	$147.65	4.659%	$154.529	$154.53	$154.55	$154.50
Purchase #7	$42.70	12.137%	$47.8825	$47.88	$47.90	$47.90
7 purchase totals =	$408.61		$440.1845	$440.19	$440.25	$440.20