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	$144.77	3.832%	$150.3176	$150.32	$150.30	$150.30
Purchase #2	$164.60	3.640%	$170.5914	$170.59	$170.60	$170.60
Purchase #3	$51.59	8.410%	$55.9287	$55.93	$55.95	$55.90
Purchase #4	$74.63	8.865%	$81.2459	$81.25	$81.25	$81.20
Purchase #5	$105.90	5.643%	$111.8759	$111.88	$111.90	$111.90
Purchase #6	$40.34	5.670%	$42.6273	$42.63	$42.65	$42.60
Purchase #7	$105.74	7.320%	$113.4802	$113.48	$113.50	$113.50
7 purchase totals =	$687.57		$726.0670	$726.08	$726.15	$726.00