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	$145.45	4.754%	$152.3647	$152.36	$152.35	$152.40
Purchase #2	$138.46	12.345%	$155.5529	$155.55	$155.55	$155.60
Purchase #3	$151.81	5.719%	$160.492	$160.49	$160.50	$160.50
Purchase #4	$216.31	7.501%	$232.5354	$232.54	$232.55	$232.50
Purchase #5	$243.61	9.434%	$266.5922	$266.59	$266.60	$266.60
Purchase #6	$143.52	9.286%	$156.8473	$156.85	$156.85	$156.80
Purchase #7	$41.88	3.648%	$43.4078	$43.41	$43.40	$43.40
7 purchase totals =	$1,081.04		$1,167.7923	$1,167.79	$1,167.80	$1,167.80