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	$207.74	4.611%	$217.3189	$217.32	$217.30	$217.30
Purchase #2	$177.82	7.466%	$191.096	$191.10	$191.10	$191.10
Purchase #3	$179.29	3.620%	$185.7803	$185.78	$185.80	$185.80
Purchase #4	$165.37	5.161%	$173.9047	$173.90	$173.90	$173.90
Purchase #5	$73.86	5.624%	$78.0139	$78.01	$78.00	$78.00
Purchase #6	$138.91	7.593%	$149.4574	$149.46	$149.45	$149.50
Purchase #7	$68.28	5.150%	$71.7964	$71.80	$71.80	$71.80
7 purchase totals =	$1,011.27		$1,067.3676	$1,067.37	$1,067.35	$1,067.40