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	$106.66	11.150%	$118.5526	$118.55	$118.55	$118.60
Purchase #2	$51.39	8.410%	$55.7119	$55.71	$55.70	$55.70
Purchase #3	$61.86	5.267%	$65.1182	$65.12	$65.10	$65.10
Purchase #4	$67.82	5.351%	$71.449	$71.45	$71.45	$71.40
Purchase #5	$7.72	13.648%	$8.7736	$8.77	$8.75	$8.80
Purchase #6	$25.39	7.411%	$27.2717	$27.27	$27.25	$27.30
Purchase #7	$247.56	9.570%	$271.2515	$271.25	$271.25	$271.30
7 purchase totals =	$568.40		$618.1285	$618.12	$618.05	$618.20