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	$169.44	11.550%	$189.0103	$189.01	$189.00	$189.00
Purchase #2	$43.97	7.800%	$47.3997	$47.40	$47.40	$47.40
Purchase #3	$139.68	4.386%	$145.8064	$145.81	$145.80	$145.80
Purchase #4	$242.93	13.404%	$275.4923	$275.49	$275.50	$275.50
Purchase #5	$176.47	11.397%	$196.5823	$196.58	$196.60	$196.60
Purchase #6	$96.93	9.666%	$106.2993	$106.30	$106.30	$106.30
Purchase #7	$164.29	11.757%	$183.6056	$183.61	$183.60	$183.60
7 purchase totals =	$1,033.71		$1,144.1959	$1,144.20	$1,144.20	$1,144.20