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	$70.77	10.124%	$77.9348	$77.93	$77.95	$77.90
Purchase #2	$73.47	4.619%	$76.8636	$76.86	$76.85	$76.90
Purchase #3	$37.72	10.868%	$41.8194	$41.82	$41.80	$41.80
Purchase #4	$94.78	3.441%	$98.0414	$98.04	$98.05	$98.00
Purchase #5	$235.76	10.130%	$259.6425	$259.64	$259.65	$259.60
Purchase #6	$34.60	9.626%	$37.9306	$37.93	$37.95	$37.90
Purchase #7	$119.46	9.212%	$130.4647	$130.46	$130.45	$130.50
7 purchase totals =	$666.56		$722.6970	$722.68	$722.70	$722.60