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	$189.39	6.679%	$202.0394	$202.04	$202.05	$202.00
Purchase #2	$160.31	11.657%	$178.9973	$179.00	$179.00	$179.00
Purchase #3	$247.94	13.659%	$281.8061	$281.81	$281.80	$281.80
Purchase #4	$119.55	3.206%	$123.3828	$123.38	$123.40	$123.40
Purchase #5	$49.51	5.535%	$52.2504	$52.25	$52.25	$52.30
Purchase #6	$78.40	5.181%	$82.4619	$82.46	$82.45	$82.50
Purchase #7	$94.92	3.860%	$98.5839	$98.58	$98.60	$98.60
7 purchase totals =	$940.02		$1,019.5218	$1,019.52	$1,019.55	$1,019.60