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	$156.49	3.825%	$162.4757	$162.48	$162.50	$162.50
Purchase #2	$146.85	9.311%	$160.5232	$160.52	$160.50	$160.50
Purchase #3	$65.35	10.396%	$72.1438	$72.14	$72.15	$72.10
Purchase #4	$195.44	5.623%	$206.4296	$206.43	$206.45	$206.40
Purchase #5	$87.52	9.349%	$95.7022	$95.70	$95.70	$95.70
Purchase #6	$208.50	7.560%	$224.2626	$224.26	$224.25	$224.30
Purchase #7	$85.82	7.617%	$92.3569	$92.36	$92.35	$92.40
7 purchase totals =	$945.97		$1,013.8940	$1,013.89	$1,013.90	$1,013.90