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	$106.40	9.139%	$116.1239	$116.12	$116.10	$116.10
Purchase #2	$114.94	3.680%	$119.1698	$119.17	$119.15	$119.20
Purchase #3	$135.29	4.308%	$141.1183	$141.12	$141.10	$141.10
Purchase #4	$42.55	12.274%	$47.7726	$47.77	$47.75	$47.80
Purchase #5	$46.27	4.193%	$48.2101	$48.21	$48.20	$48.20
Purchase #6	$85.87	4.609%	$89.8277	$89.83	$89.85	$89.80
Purchase #7	$136.90	6.814%	$146.2284	$146.23	$146.25	$146.20
7 purchase totals =	$668.22		$708.4508	$708.45	$708.40	$708.40