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	$57.71	3.555%	$59.7616	$59.76	$59.75	$59.80
Purchase #2	$191.30	9.194%	$208.8881	$208.89	$208.90	$208.90
Purchase #3	$32.25	12.623%	$36.3209	$36.32	$36.30	$36.30
Purchase #4	$74.96	6.500%	$79.8324	$79.83	$79.85	$79.80
Purchase #5	$173.27	5.359%	$182.5555	$182.56	$182.55	$182.60
Purchase #6	$240.99	7.660%	$259.4498	$259.45	$259.45	$259.40
Purchase #7	$139.85	10.204%	$154.1203	$154.12	$154.10	$154.10
7 purchase totals =	$910.33		$980.9286	$980.93	$980.90	$980.90