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	$167.62	6.124%	$177.885	$177.89	$177.90	$177.90
Purchase #2	$169.65	5.828%	$179.5372	$179.54	$179.55	$179.50
Purchase #3	$186.75	11.521%	$208.2655	$208.27	$208.25	$208.30
Purchase #4	$127.30	5.726%	$134.5892	$134.59	$134.60	$134.60
Purchase #5	$79.85	13.527%	$90.6513	$90.65	$90.65	$90.70
Purchase #6	$164.40	7.143%	$176.1431	$176.14	$176.15	$176.10
Purchase #7	$49.37	11.641%	$55.1172	$55.12	$55.10	$55.10
7 purchase totals =	$944.94		$1,022.1885	$1,022.20	$1,022.20	$1,022.20