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	$65.81	5.392%	$69.3585	$69.36	$69.35	$69.40
Purchase #2	$83.68	9.692%	$91.7903	$91.79	$91.80	$91.80
Purchase #3	$91.52	10.858%	$101.4572	$101.46	$101.45	$101.50
Purchase #4	$100.88	5.418%	$106.3457	$106.35	$106.35	$106.30
Purchase #5	$227.32	12.577%	$255.91	$255.91	$255.90	$255.90
Purchase #6	$104.54	7.667%	$112.5551	$112.56	$112.55	$112.60
Purchase #7	$37.97	5.460%	$40.0432	$40.04	$40.05	$40.00
7 purchase totals =	$711.72		$777.4600	$777.47	$777.45	$777.50