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	$60.67	11.189%	$67.4584	$67.46	$67.45	$67.50
Purchase #2	$109.82	8.237%	$118.8659	$118.87	$118.85	$118.90
Purchase #3	$91.91	6.762%	$98.125	$98.13	$98.15	$98.10
Purchase #4	$93.91	7.238%	$100.7072	$100.71	$100.70	$100.70
Purchase #5	$55.68	6.661%	$59.3888	$59.39	$59.40	$59.40
Purchase #6	$167.51	7.808%	$180.5892	$180.59	$180.60	$180.60
Purchase #7	$227.51	8.317%	$246.432	$246.43	$246.45	$246.40
7 purchase totals =	$807.01		$871.5665	$871.58	$871.60	$871.60