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	$62.73	12.576%	$70.6189	$70.62	$70.60	$70.60
Purchase #2	$169.87	6.388%	$180.7213	$180.72	$180.70	$180.70
Purchase #3	$171.99	7.253%	$184.4644	$184.46	$184.45	$184.50
Purchase #4	$225.53	13.709%	$256.4479	$256.45	$256.45	$256.40
Purchase #5	$54.74	8.617%	$59.4569	$59.46	$59.45	$59.50
Purchase #6	$102.98	10.660%	$113.9577	$113.96	$113.95	$114.00
Purchase #7	$156.38	3.742%	$162.2317	$162.23	$162.25	$162.20
7 purchase totals =	$944.22		$1,027.8988	$1,027.90	$1,027.85	$1,027.90