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	$57.86	9.192%	$63.1785	$63.18	$63.20	$63.20
Purchase #2	$41.45	3.529%	$42.9128	$42.91	$42.90	$42.90
Purchase #3	$54.70	8.209%	$59.1903	$59.19	$59.20	$59.20
Purchase #4	$15.81	11.443%	$17.6191	$17.62	$17.60	$17.60
Purchase #5	$144.80	7.498%	$155.6571	$155.66	$155.65	$155.70
Purchase #6	$169.52	12.228%	$190.2489	$190.25	$190.25	$190.20
Purchase #7	$93.69	10.810%	$103.8179	$103.82	$103.80	$103.80
7 purchase totals =	$577.83		$632.6246	$632.63	$632.60	$632.60