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	$68.58	5.149%	$72.1112	$72.11	$72.10	$72.10
Purchase #2	$99.43	10.275%	$109.6464	$109.65	$109.65	$109.60
Purchase #3	$113.64	3.684%	$117.8265	$117.83	$117.85	$117.80
Purchase #4	$106.30	3.218%	$109.7207	$109.72	$109.70	$109.70
Purchase #5	$146.30	6.638%	$156.0114	$156.01	$156.00	$156.00
Purchase #6	$52.25	4.315%	$54.5046	$54.50	$54.50	$54.50
Purchase #7	$60.74	8.248%	$65.7498	$65.75	$65.75	$65.70
7 purchase totals =	$647.24		$685.5706	$685.57	$685.55	$685.40