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	$145.87	13.167%	$165.0767	$165.08	$165.10	$165.10
Purchase #2	$119.52	11.723%	$133.5313	$133.53	$133.55	$133.50
Purchase #3	$92.74	13.800%	$105.5381	$105.54	$105.55	$105.50
Purchase #4	$228.72	7.847%	$246.6677	$246.67	$246.65	$246.70
Purchase #5	$95.26	5.319%	$100.3269	$100.33	$100.35	$100.30
Purchase #6	$172.80	8.404%	$187.3221	$187.32	$187.30	$187.30
Purchase #7	$155.88	9.850%	$171.2342	$171.23	$171.25	$171.20
7 purchase totals =	$1,010.79		$1,109.6970	$1,109.70	$1,109.75	$1,109.60