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	$166.62	5.334%	$175.5075	$175.51	$175.50	$175.50
Purchase #2	$182.88	4.158%	$190.4842	$190.48	$190.50	$190.50
Purchase #3	$240.67	3.440%	$248.949	$248.95	$248.95	$248.90
Purchase #4	$204.60	13.117%	$231.4374	$231.44	$231.45	$231.40
Purchase #5	$128.38	11.610%	$143.2849	$143.28	$143.30	$143.30
Purchase #6	$107.60	4.584%	$112.5324	$112.53	$112.55	$112.50
Purchase #7	$136.39	9.134%	$148.8479	$148.85	$148.85	$148.80
7 purchase totals =	$1,167.14		$1,251.0433	$1,251.04	$1,251.10	$1,250.90