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	$98.91	6.716%	$105.5528	$105.55	$105.55	$105.60
Purchase #2	$90.79	9.864%	$99.7455	$99.75	$99.75	$99.70
Purchase #3	$198.65	6.409%	$211.3815	$211.38	$211.40	$211.40
Purchase #4	$51.87	7.629%	$55.8272	$55.83	$55.85	$55.80
Purchase #5	$182.52	5.365%	$192.3122	$192.31	$192.30	$192.30
Purchase #6	$246.25	6.708%	$262.7685	$262.77	$262.75	$262.80
Purchase #7	$76.26	8.124%	$82.4554	$82.46	$82.45	$82.50
7 purchase totals =	$945.25		$1,010.0431	$1,010.05	$1,010.05	$1,010.10