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	$25.61	12.187%	$28.7311	$28.73	$28.75	$28.70
Purchase #2	$13.73	4.282%	$14.3179	$14.32	$14.30	$14.30
Purchase #3	$172.91	13.368%	$196.0246	$196.02	$196.00	$196.00
Purchase #4	$140.90	3.699%	$146.1119	$146.11	$146.10	$146.10
Purchase #5	$132.62	10.471%	$146.5066	$146.51	$146.50	$146.50
Purchase #6	$129.35	6.419%	$137.653	$137.65	$137.65	$137.70
Purchase #7	$59.26	4.849%	$62.1335	$62.13	$62.15	$62.10
7 purchase totals =	$674.38		$731.4786	$731.47	$731.45	$731.40