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	$224.37	9.859%	$246.4906	$246.49	$246.50	$246.50
Purchase #2	$52.98	5.414%	$55.8483	$55.85	$55.85	$55.80
Purchase #3	$119.51	3.374%	$123.5423	$123.54	$123.55	$123.50
Purchase #4	$148.29	4.224%	$154.5538	$154.55	$154.55	$154.60
Purchase #5	$100.71	11.554%	$112.346	$112.35	$112.35	$112.30
Purchase #6	$212.36	11.497%	$236.775	$236.78	$236.80	$236.80
Purchase #7	$82.90	8.212%	$89.7077	$89.71	$89.70	$89.70
7 purchase totals =	$941.12		$1,019.2637	$1,019.27	$1,019.30	$1,019.20