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	$115.76	8.781%	$125.9249	$125.92	$125.90	$125.90
Purchase #2	$105.81	12.199%	$118.7178	$118.72	$118.70	$118.70
Purchase #3	$53.65	10.280%	$59.1652	$59.17	$59.15	$59.20
Purchase #4	$69.34	4.551%	$72.4957	$72.50	$72.50	$72.50
Purchase #5	$225.78	9.274%	$246.7188	$246.72	$246.70	$246.70
Purchase #6	$117.30	12.564%	$132.0376	$132.04	$132.05	$132.00
Purchase #7	$68.60	4.605%	$71.759	$71.76	$71.75	$71.80
7 purchase totals =	$756.24		$826.8190	$826.83	$826.75	$826.80