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	$91.95	12.764%	$103.6865	$103.69	$103.70	$103.70
Purchase #2	$193.39	8.458%	$209.7469	$209.75	$209.75	$209.70
Purchase #3	$178.75	5.337%	$188.2899	$188.29	$188.30	$188.30
Purchase #4	$158.67	10.154%	$174.7814	$174.78	$174.80	$174.80
Purchase #5	$177.39	4.373%	$185.1473	$185.15	$185.15	$185.10
Purchase #6	$148.91	13.517%	$169.0382	$169.04	$169.05	$169.00
Purchase #7	$160.57	3.427%	$166.0727	$166.07	$166.05	$166.10
7 purchase totals =	$1,109.63		$1,196.7629	$1,196.77	$1,196.80	$1,196.70