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	$109.63	7.315%	$117.6494	$117.65	$117.65	$117.60
Purchase #2	$112.27	12.580%	$126.3936	$126.39	$126.40	$126.40
Purchase #3	$163.45	10.850%	$181.1843	$181.18	$181.20	$181.20
Purchase #4	$90.82	10.745%	$100.5786	$100.58	$100.60	$100.60
Purchase #5	$165.27	8.731%	$179.6997	$179.70	$179.70	$179.70
Purchase #6	$114.82	7.307%	$123.2099	$123.21	$123.20	$123.20
Purchase #7	$212.54	9.568%	$232.8758	$232.88	$232.90	$232.90
7 purchase totals =	$968.80		$1,061.5913	$1,061.59	$1,061.65	$1,061.60