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	$189.80	5.527%	$200.2902	$200.29	$200.30	$200.30
Purchase #2	$175.98	3.641%	$182.3874	$182.39	$182.40	$182.40
Purchase #3	$89.59	13.685%	$101.8504	$101.85	$101.85	$101.90
Purchase #4	$174.93	7.293%	$187.6876	$187.69	$187.70	$187.70
Purchase #5	$94.50	4.187%	$98.4567	$98.46	$98.45	$98.50
Purchase #6	$27.94	6.387%	$29.7245	$29.72	$29.70	$29.70
Purchase #7	$185.63	11.436%	$206.8586	$206.86	$206.85	$206.90
7 purchase totals =	$938.37		$1,007.2554	$1,007.26	$1,007.25	$1,007.40