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	$239.26	11.501%	$266.7773	$266.78	$266.80	$266.80
Purchase #2	$197.42	13.672%	$224.4113	$224.41	$224.40	$224.40
Purchase #3	$202.88	6.319%	$215.7	$215.70	$215.70	$215.70
Purchase #4	$53.57	11.665%	$59.8189	$59.82	$59.80	$59.80
Purchase #5	$139.41	8.211%	$150.857	$150.86	$150.85	$150.90
Purchase #6	$60.47	7.490%	$64.9992	$65.00	$65.00	$65.00
Purchase #7	$98.62	4.154%	$102.7167	$102.72	$102.70	$102.70
7 purchase totals =	$991.63		$1,085.2804	$1,085.29	$1,085.25	$1,085.30