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	$52.90	3.690%	$54.852	$54.85	$54.85	$54.90
Purchase #2	$195.31	8.439%	$211.7922	$211.79	$211.80	$211.80
Purchase #3	$139.53	6.311%	$148.3357	$148.34	$148.35	$148.30
Purchase #4	$118.95	4.619%	$124.4443	$124.44	$124.45	$124.40
Purchase #5	$215.25	7.553%	$231.5078	$231.51	$231.50	$231.50
Purchase #6	$158.28	13.676%	$179.9264	$179.93	$179.95	$179.90
Purchase #7	$101.53	12.696%	$114.4202	$114.42	$114.40	$114.40
7 purchase totals =	$981.75		$1,065.2786	$1,065.28	$1,065.30	$1,065.20