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	$65.76	10.726%	$72.8134	$72.81	$72.80	$72.80
Purchase #2	$48.48	8.736%	$52.7152	$52.72	$52.70	$52.70
Purchase #3	$178.83	5.496%	$188.6585	$188.66	$188.65	$188.70
Purchase #4	$191.64	9.661%	$210.1543	$210.15	$210.15	$210.20
Purchase #5	$189.55	8.578%	$205.8096	$205.81	$205.80	$205.80
Purchase #6	$191.70	12.636%	$215.9232	$215.92	$215.90	$215.90
Purchase #7	$234.45	10.666%	$259.4564	$259.46	$259.45	$259.50
7 purchase totals =	$1,100.41		$1,205.5306	$1,205.53	$1,205.45	$1,205.60