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	$14.32	11.307%	$15.9392	$15.94	$15.95	$15.90
Purchase #2	$96.49	4.597%	$100.9256	$100.93	$100.95	$100.90
Purchase #3	$211.76	12.167%	$237.5248	$237.52	$237.50	$237.50
Purchase #4	$167.34	8.289%	$181.2108	$181.21	$181.20	$181.20
Purchase #5	$231.65	10.320%	$255.5563	$255.56	$255.55	$255.60
Purchase #6	$110.86	4.112%	$115.4186	$115.42	$115.40	$115.40
Purchase #7	$127.62	4.545%	$133.4203	$133.42	$133.40	$133.40
7 purchase totals =	$960.04		$1,039.9956	$1,040.00	$1,039.95	$1,039.90