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	$208.61	6.689%	$222.5639	$222.56	$222.55	$222.60
Purchase #2	$52.32	13.591%	$59.4308	$59.43	$59.45	$59.40
Purchase #3	$111.43	4.692%	$116.6583	$116.66	$116.65	$116.70
Purchase #4	$214.71	8.544%	$233.0548	$233.05	$233.05	$233.10
Purchase #5	$34.48	5.367%	$36.3305	$36.33	$36.35	$36.30
Purchase #6	$223.50	3.508%	$231.3404	$231.34	$231.35	$231.30
Purchase #7	$103.98	9.312%	$113.6626	$113.66	$113.65	$113.70
7 purchase totals =	$949.03		$1,013.0413	$1,013.03	$1,013.05	$1,013.10