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	$224.75	13.723%	$255.5924	$255.59	$255.60	$255.60
Purchase #2	$17.41	13.850%	$19.8213	$19.82	$19.80	$19.80
Purchase #3	$103.70	9.712%	$113.7713	$113.77	$113.75	$113.80
Purchase #4	$250.36	7.282%	$268.5912	$268.59	$268.60	$268.60
Purchase #5	$220.34	13.567%	$250.2335	$250.23	$250.25	$250.20
Purchase #6	$97.95	7.755%	$105.546	$105.55	$105.55	$105.50
Purchase #7	$225.62	8.795%	$245.4633	$245.46	$245.45	$245.50
7 purchase totals =	$1,140.13		$1,259.0190	$1,259.01	$1,259.00	$1,259.00