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	$107.71	4.638%	$112.7056	$112.71	$112.70	$112.70
Purchase #2	$65.26	10.586%	$72.1684	$72.17	$72.15	$72.20
Purchase #3	$77.41	7.150%	$82.9448	$82.94	$82.95	$82.90
Purchase #4	$166.84	8.384%	$180.8279	$180.83	$180.85	$180.80
Purchase #5	$146.46	13.558%	$166.317	$166.32	$166.30	$166.30
Purchase #6	$179.95	10.549%	$198.9329	$198.93	$198.95	$198.90
Purchase #7	$60.64	9.498%	$66.3996	$66.40	$66.40	$66.40
7 purchase totals =	$804.27		$880.2962	$880.30	$880.30	$880.20