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	$99.33	6.434%	$105.7209	$105.72	$105.70	$105.70
Purchase #2	$198.83	13.334%	$225.342	$225.34	$225.35	$225.30
Purchase #3	$98.51	3.694%	$102.149	$102.15	$102.15	$102.10
Purchase #4	$209.93	12.641%	$236.4673	$236.47	$236.45	$236.50
Purchase #5	$97.35	9.470%	$106.569	$106.57	$106.55	$106.60
Purchase #6	$99.51	7.168%	$106.6429	$106.64	$106.65	$106.60
Purchase #7	$178.70	5.798%	$189.061	$189.06	$189.05	$189.10
7 purchase totals =	$982.16		$1,071.9521	$1,071.95	$1,071.90	$1,071.90