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	$133.25	8.412%	$144.459	$144.46	$144.45	$144.50
Purchase #2	$80.80	12.212%	$90.6673	$90.67	$90.65	$90.70
Purchase #3	$237.81	4.682%	$248.9443	$248.94	$248.95	$248.90
Purchase #4	$89.66	11.348%	$99.8346	$99.83	$99.85	$99.80
Purchase #5	$185.86	9.458%	$203.4386	$203.44	$203.45	$203.40
Purchase #6	$120.55	11.293%	$134.1637	$134.16	$134.15	$134.20
Purchase #7	$86.29	6.175%	$91.6184	$91.62	$91.60	$91.60
7 purchase totals =	$934.22		$1,013.1259	$1,013.12	$1,013.10	$1,013.10