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	$56.88	4.233%	$59.2877	$59.29	$59.30	$59.30
Purchase #2	$152.61	4.370%	$159.2791	$159.28	$159.30	$159.30
Purchase #3	$217.99	4.304%	$227.3723	$227.37	$227.35	$227.40
Purchase #4	$237.78	7.615%	$255.8869	$255.89	$255.90	$255.90
Purchase #5	$207.54	3.124%	$214.0235	$214.02	$214.00	$214.00
Purchase #6	$242.98	6.439%	$258.6255	$258.63	$258.65	$258.60
Purchase #7	$87.75	13.397%	$99.5059	$99.51	$99.50	$99.50
7 purchase totals =	$1,203.53		$1,273.9809	$1,273.99	$1,274.00	$1,274.00