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	$185.56	5.864%	$196.4412	$196.44	$196.45	$196.40
Purchase #2	$225.87	13.535%	$256.4415	$256.44	$256.45	$256.40
Purchase #3	$227.57	11.296%	$253.2763	$253.28	$253.30	$253.30
Purchase #4	$177.64	7.610%	$191.1584	$191.16	$191.15	$191.20
Purchase #5	$127.30	11.765%	$142.2768	$142.28	$142.30	$142.30
Purchase #6	$182.53	12.624%	$205.5726	$205.57	$205.55	$205.60
Purchase #7	$176.68	9.313%	$193.1342	$193.13	$193.15	$193.10
7 purchase totals =	$1,303.15		$1,438.3010	$1,438.30	$1,438.35	$1,438.30