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	$185.75	13.319%	$210.49	$210.49	$210.50	$210.50
Purchase #2	$245.46	10.848%	$272.0875	$272.09	$272.10	$272.10
Purchase #3	$42.96	13.155%	$48.6114	$48.61	$48.60	$48.60
Purchase #4	$56.86	4.790%	$59.5836	$59.58	$59.60	$59.60
Purchase #5	$226.54	6.736%	$241.7997	$241.80	$241.80	$241.80
Purchase #6	$89.94	9.746%	$98.7056	$98.71	$98.70	$98.70
Purchase #7	$231.88	8.285%	$251.0913	$251.09	$251.10	$251.10
7 purchase totals =	$1,079.39		$1,182.3691	$1,182.37	$1,182.40	$1,182.40