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	$223.33	11.783%	$249.645	$249.65	$249.65	$249.60
Purchase #2	$35.36	5.715%	$37.3808	$37.38	$37.40	$37.40
Purchase #3	$109.95	6.873%	$117.5069	$117.51	$117.50	$117.50
Purchase #4	$132.39	5.694%	$139.9283	$139.93	$139.95	$139.90
Purchase #5	$84.37	9.154%	$92.0932	$92.09	$92.10	$92.10
Purchase #6	$80.43	11.697%	$89.8379	$89.84	$89.85	$89.80
Purchase #7	$48.32	9.737%	$53.0249	$53.02	$53.00	$53.00
7 purchase totals =	$714.15		$779.4170	$779.42	$779.45	$779.30