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	$183.46	4.313%	$191.3726	$191.37	$191.35	$191.40
Purchase #2	$213.74	13.396%	$242.3726	$242.37	$242.35	$242.40
Purchase #3	$98.69	5.504%	$104.1219	$104.12	$104.10	$104.10
Purchase #4	$105.64	3.192%	$109.012	$109.01	$109.00	$109.00
Purchase #5	$134.75	3.691%	$139.7236	$139.72	$139.70	$139.70
Purchase #6	$186.34	7.724%	$200.7329	$200.73	$200.75	$200.70
Purchase #7	$60.85	4.559%	$63.6242	$63.62	$63.60	$63.60
7 purchase totals =	$983.47		$1,050.9598	$1,050.94	$1,050.85	$1,050.90