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	$176.99	10.261%	$195.1509	$195.15	$195.15	$195.20
Purchase #2	$18.48	11.230%	$20.5553	$20.56	$20.55	$20.60
Purchase #3	$133.25	10.724%	$147.5397	$147.54	$147.55	$147.50
Purchase #4	$18.94	4.759%	$19.8414	$19.84	$19.85	$19.80
Purchase #5	$101.90	3.553%	$105.5205	$105.52	$105.50	$105.50
Purchase #6	$13.40	7.587%	$14.4167	$14.42	$14.40	$14.40
Purchase #7	$105.38	6.751%	$112.4942	$112.49	$112.50	$112.50
7 purchase totals =	$568.34		$615.5187	$615.52	$615.50	$615.50