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	$227.89	6.841%	$243.48	$243.48	$243.50	$243.50
Purchase #2	$124.30	12.284%	$139.569	$139.57	$139.55	$139.60
Purchase #3	$176.79	7.864%	$190.6928	$190.69	$190.70	$190.70
Purchase #4	$169.75	3.182%	$175.1514	$175.15	$175.15	$175.20
Purchase #5	$190.46	7.717%	$205.1578	$205.16	$205.15	$205.20
Purchase #6	$9.83	5.385%	$10.3593	$10.36	$10.35	$10.40
Purchase #7	$117.67	4.659%	$123.1522	$123.15	$123.15	$123.20
7 purchase totals =	$1,016.69		$1,087.5625	$1,087.56	$1,087.55	$1,087.80