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	$39.29	10.567%	$43.4418	$43.44	$43.45	$43.40
Purchase #2	$156.59	9.283%	$171.1262	$171.13	$171.15	$171.10
Purchase #3	$162.29	13.186%	$183.6896	$183.69	$183.70	$183.70
Purchase #4	$177.64	7.817%	$191.5261	$191.53	$191.55	$191.50
Purchase #5	$99.34	3.290%	$102.6083	$102.61	$102.60	$102.60
Purchase #6	$173.86	5.389%	$183.2293	$183.23	$183.25	$183.20
Purchase #7	$136.82	12.445%	$153.8472	$153.85	$153.85	$153.80
7 purchase totals =	$945.83		$1,029.4685	$1,029.48	$1,029.55	$1,029.30