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	$186.57	7.405%	$200.3855	$200.39	$200.40	$200.40
Purchase #2	$133.75	6.557%	$142.52	$142.52	$142.50	$142.50
Purchase #3	$127.56	9.381%	$139.5264	$139.53	$139.55	$139.50
Purchase #4	$12.44	5.114%	$13.0762	$13.08	$13.10	$13.10
Purchase #5	$242.27	5.675%	$256.0188	$256.02	$256.00	$256.00
Purchase #6	$22.88	6.588%	$24.3873	$24.39	$24.40	$24.40
Purchase #7	$69.43	12.453%	$78.0761	$78.08	$78.10	$78.10
7 purchase totals =	$794.90		$853.9903	$854.01	$854.05	$854.00