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	$212.35	4.329%	$221.5426	$221.54	$221.55	$221.50
Purchase #2	$189.77	10.150%	$209.0317	$209.03	$209.05	$209.00
Purchase #3	$111.45	6.685%	$118.9004	$118.90	$118.90	$118.90
Purchase #4	$98.70	13.181%	$111.7096	$111.71	$111.70	$111.70
Purchase #5	$100.86	5.820%	$106.7301	$106.73	$106.75	$106.70
Purchase #6	$106.68	4.446%	$111.423	$111.42	$111.40	$111.40
Purchase #7	$94.97	12.315%	$106.6656	$106.67	$106.65	$106.70
7 purchase totals =	$914.78		$986.0030	$986.00	$986.00	$985.90