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	$21.43	10.411%	$23.6611	$23.66	$23.65	$23.70
Purchase #2	$85.52	4.486%	$89.3564	$89.36	$89.35	$89.40
Purchase #3	$220.54	6.547%	$234.9788	$234.98	$235.00	$235.00
Purchase #4	$150.77	11.282%	$167.7799	$167.78	$167.80	$167.80
Purchase #5	$246.56	12.271%	$276.8154	$276.82	$276.80	$276.80
Purchase #6	$221.94	6.536%	$236.446	$236.45	$236.45	$236.40
Purchase #7	$77.93	3.256%	$80.4674	$80.47	$80.45	$80.50
7 purchase totals =	$1,024.69		$1,109.5050	$1,109.52	$1,109.50	$1,109.60