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	$107.86	3.723%	$111.8756	$111.88	$111.90	$111.90
Purchase #2	$164.65	6.564%	$175.4576	$175.46	$175.45	$175.50
Purchase #3	$105.70	3.581%	$109.4851	$109.49	$109.50	$109.50
Purchase #4	$111.26	4.315%	$116.0609	$116.06	$116.05	$116.10
Purchase #5	$90.74	3.134%	$93.5838	$93.58	$93.60	$93.60
Purchase #6	$168.60	12.767%	$190.1252	$190.13	$190.15	$190.10
Purchase #7	$44.56	9.331%	$48.7179	$48.72	$48.70	$48.70
7 purchase totals =	$793.37		$845.3061	$845.32	$845.35	$845.40