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	$111.82	7.377%	$120.069	$120.07	$120.05	$120.10
Purchase #2	$81.39	11.651%	$90.8727	$90.87	$90.85	$90.90
Purchase #3	$187.75	13.511%	$213.1169	$213.12	$213.10	$213.10
Purchase #4	$158.82	8.649%	$172.5563	$172.56	$172.55	$172.60
Purchase #5	$69.36	11.520%	$77.3503	$77.35	$77.35	$77.40
Purchase #6	$100.61	4.736%	$105.3749	$105.37	$105.35	$105.40
Purchase #7	$215.80	7.260%	$231.4671	$231.47	$231.45	$231.50
7 purchase totals =	$925.55		$1,010.8072	$1,010.81	$1,010.70	$1,011.00