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	$159.25	6.214%	$169.1458	$169.15	$169.15	$169.10
Purchase #2	$91.37	6.167%	$97.0048	$97.00	$97.00	$97.00
Purchase #3	$56.77	7.371%	$60.9545	$60.95	$60.95	$61.00
Purchase #4	$103.28	13.724%	$117.4541	$117.45	$117.45	$117.50
Purchase #5	$236.79	6.363%	$251.8569	$251.86	$251.85	$251.90
Purchase #6	$71.47	9.751%	$78.439	$78.44	$78.45	$78.40
Purchase #7	$93.50	7.592%	$100.5985	$100.60	$100.60	$100.60
7 purchase totals =	$812.43		$875.4536	$875.45	$875.45	$875.50