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	$61.62	6.828%	$65.8274	$65.83	$65.85	$65.80
Purchase #2	$80.50	12.712%	$90.7332	$90.73	$90.75	$90.70
Purchase #3	$213.84	13.713%	$243.1639	$243.16	$243.15	$243.20
Purchase #4	$123.39	10.484%	$136.3262	$136.33	$136.35	$136.30
Purchase #5	$145.37	4.589%	$152.041	$152.04	$152.05	$152.00
Purchase #6	$19.45	11.223%	$21.6329	$21.63	$21.65	$21.60
Purchase #7	$56.71	9.467%	$62.0787	$62.08	$62.10	$62.10
7 purchase totals =	$700.88		$771.8033	$771.80	$771.90	$771.70