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	$129.54	9.675%	$142.073	$142.07	$142.05	$142.10
Purchase #2	$50.65	4.378%	$52.8675	$52.87	$52.85	$52.90
Purchase #3	$58.64	3.850%	$60.8976	$60.90	$60.90	$60.90
Purchase #4	$101.39	4.225%	$105.6737	$105.67	$105.65	$105.70
Purchase #5	$108.78	4.446%	$113.6164	$113.62	$113.60	$113.60
Purchase #6	$167.65	4.353%	$174.9478	$174.95	$174.95	$174.90
Purchase #7	$80.85	7.363%	$86.803	$86.80	$86.80	$86.80
7 purchase totals =	$697.50		$736.8790	$736.88	$736.80	$736.90