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	$148.49	11.408%	$165.4297	$165.43	$165.45	$165.40
Purchase #2	$174.67	4.352%	$182.2716	$182.27	$182.25	$182.30
Purchase #3	$29.37	12.437%	$33.0227	$33.02	$33.00	$33.00
Purchase #4	$123.75	7.190%	$132.6476	$132.65	$132.65	$132.60
Purchase #5	$145.60	6.119%	$154.5093	$154.51	$154.50	$154.50
Purchase #6	$92.81	13.358%	$105.2076	$105.21	$105.20	$105.20
Purchase #7	$150.54	7.806%	$162.2912	$162.29	$162.30	$162.30
7 purchase totals =	$865.23		$935.3797	$935.38	$935.35	$935.30