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	$209.61	10.212%	$231.0154	$231.02	$231.00	$231.00
Purchase #2	$223.91	9.633%	$245.4793	$245.48	$245.50	$245.50
Purchase #3	$235.50	12.770%	$265.5734	$265.57	$265.55	$265.60
Purchase #4	$227.61	4.618%	$238.121	$238.12	$238.10	$238.10
Purchase #5	$100.94	13.871%	$114.9414	$114.94	$114.95	$114.90
Purchase #6	$205.86	9.615%	$225.6534	$225.65	$225.65	$225.70
Purchase #7	$240.35	6.249%	$255.3695	$255.37	$255.35	$255.40
7 purchase totals =	$1,443.78		$1,576.1534	$1,576.15	$1,576.10	$1,576.20