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	$229.37	7.487%	$246.5429	$246.54	$246.55	$246.50
Purchase #2	$151.32	9.283%	$165.367	$165.37	$165.35	$165.40
Purchase #3	$231.63	12.834%	$261.3574	$261.36	$261.35	$261.40
Purchase #4	$58.55	5.218%	$61.6051	$61.61	$61.60	$61.60
Purchase #5	$151.52	9.356%	$165.6962	$165.70	$165.70	$165.70
Purchase #6	$55.49	12.808%	$62.5972	$62.60	$62.60	$62.60
Purchase #7	$146.35	6.311%	$155.5861	$155.59	$155.60	$155.60
7 purchase totals =	$1,024.23		$1,118.7519	$1,118.77	$1,118.75	$1,118.80