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	$134.66	3.863%	$139.8619	$139.86	$139.85	$139.90
Purchase #2	$76.49	9.322%	$83.6204	$83.62	$83.60	$83.60
Purchase #3	$199.87	13.870%	$227.592	$227.59	$227.60	$227.60
Purchase #4	$223.64	13.374%	$253.5496	$253.55	$253.55	$253.50
Purchase #5	$135.52	7.142%	$145.1988	$145.20	$145.20	$145.20
Purchase #6	$103.30	11.150%	$114.818	$114.82	$114.80	$114.80
Purchase #7	$163.26	7.116%	$174.8776	$174.88	$174.90	$174.90
7 purchase totals =	$1,036.74		$1,139.5183	$1,139.52	$1,139.50	$1,139.50