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	$57.39	8.826%	$62.4552	$62.46	$62.45	$62.50
Purchase #2	$131.62	11.225%	$146.3943	$146.39	$146.40	$146.40
Purchase #3	$41.63	3.674%	$43.1595	$43.16	$43.15	$43.20
Purchase #4	$84.25	7.338%	$90.4323	$90.43	$90.45	$90.40
Purchase #5	$97.61	9.107%	$106.4993	$106.50	$106.50	$106.50
Purchase #6	$98.47	5.330%	$103.7185	$103.72	$103.70	$103.70
Purchase #7	$148.87	12.632%	$167.6753	$167.68	$167.70	$167.70
7 purchase totals =	$659.84		$720.3344	$720.34	$720.35	$720.40