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	$129.46	3.682%	$134.2267	$134.23	$134.25	$134.20
Purchase #2	$176.57	10.218%	$194.6119	$194.61	$194.60	$194.60
Purchase #3	$67.50	5.870%	$71.4623	$71.46	$71.45	$71.50
Purchase #4	$66.52	13.745%	$75.6632	$75.66	$75.65	$75.70
Purchase #5	$155.60	8.143%	$168.2705	$168.27	$168.25	$168.30
Purchase #6	$174.55	12.681%	$196.6847	$196.68	$196.70	$196.70
Purchase #7	$158.62	4.160%	$165.2186	$165.22	$165.20	$165.20
7 purchase totals =	$928.82		$1,006.1379	$1,006.13	$1,006.10	$1,006.20