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	$24.74	4.864%	$25.9434	$25.94	$25.95	$25.90
Purchase #2	$32.95	5.524%	$34.7702	$34.77	$34.75	$34.80
Purchase #3	$249.65	3.581%	$258.59	$258.59	$258.60	$258.60
Purchase #4	$127.47	10.206%	$140.4796	$140.48	$140.50	$140.50
Purchase #5	$108.55	13.379%	$123.0729	$123.07	$123.05	$123.10
Purchase #6	$156.91	7.666%	$168.9387	$168.94	$168.95	$168.90
Purchase #7	$116.37	5.844%	$123.1707	$123.17	$123.15	$123.20
7 purchase totals =	$816.64		$874.9655	$874.96	$874.95	$875.00