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	$127.57	10.841%	$141.3999	$141.40	$141.40	$141.40
Purchase #2	$104.94	11.732%	$117.2516	$117.25	$117.25	$117.30
Purchase #3	$248.65	12.858%	$280.6214	$280.62	$280.60	$280.60
Purchase #4	$151.28	3.721%	$156.9091	$156.91	$156.90	$156.90
Purchase #5	$159.72	13.270%	$180.9148	$180.91	$180.90	$180.90
Purchase #6	$221.82	12.872%	$250.3727	$250.37	$250.35	$250.40
Purchase #7	$90.98	12.302%	$102.1724	$102.17	$102.15	$102.20
7 purchase totals =	$1,104.96		$1,229.6419	$1,229.63	$1,229.55	$1,229.70