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	$224.48	5.363%	$236.5189	$236.52	$236.50	$236.50
Purchase #2	$20.77	3.181%	$21.4307	$21.43	$21.45	$21.40
Purchase #3	$178.43	6.133%	$189.3731	$189.37	$189.35	$189.40
Purchase #4	$250.53	12.637%	$282.1895	$282.19	$282.20	$282.20
Purchase #5	$153.66	10.840%	$170.3167	$170.32	$170.30	$170.30
Purchase #6	$6.87	8.747%	$7.4709	$7.47	$7.45	$7.50
Purchase #7	$90.33	11.357%	$100.5888	$100.59	$100.60	$100.60
7 purchase totals =	$925.07		$1,007.8886	$1,007.89	$1,007.85	$1,007.90