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	$129.69	10.372%	$143.1414	$143.14	$143.15	$143.10
Purchase #2	$191.90	8.853%	$208.8889	$208.89	$208.90	$208.90
Purchase #3	$6.41	9.788%	$7.0374	$7.04	$7.05	$7.00
Purchase #4	$153.82	5.462%	$162.2216	$162.22	$162.20	$162.20
Purchase #5	$103.52	9.176%	$113.019	$113.02	$113.00	$113.00
Purchase #6	$56.49	4.557%	$59.0642	$59.06	$59.05	$59.10
Purchase #7	$196.32	4.621%	$205.3919	$205.39	$205.40	$205.40
7 purchase totals =	$838.15		$898.7644	$898.76	$898.75	$898.70