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	$246.89	10.788%	$273.5245	$273.52	$273.50	$273.50
Purchase #2	$98.47	4.734%	$103.1316	$103.13	$103.15	$103.10
Purchase #3	$5.87	11.415%	$6.5401	$6.54	$6.55	$6.50
Purchase #4	$74.48	9.564%	$81.6033	$81.60	$81.60	$81.60
Purchase #5	$208.90	8.765%	$227.2101	$227.21	$227.20	$227.20
Purchase #6	$179.86	7.235%	$192.8729	$192.87	$192.85	$192.90
Purchase #7	$148.75	13.233%	$168.4341	$168.43	$168.45	$168.40
7 purchase totals =	$963.22		$1,053.3166	$1,053.30	$1,053.30	$1,053.20