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	$10.82	5.616%	$11.4277	$11.43	$11.45	$11.40
Purchase #2	$212.35	10.357%	$234.3431	$234.34	$234.35	$234.30
Purchase #3	$36.69	10.624%	$40.5879	$40.59	$40.60	$40.60
Purchase #4	$200.99	7.565%	$216.1949	$216.19	$216.20	$216.20
Purchase #5	$231.37	12.121%	$259.4144	$259.41	$259.40	$259.40
Purchase #6	$111.36	4.303%	$116.1518	$116.15	$116.15	$116.20
Purchase #7	$113.70	8.482%	$123.344	$123.34	$123.35	$123.30
7 purchase totals =	$917.28		$1,001.4638	$1,001.45	$1,001.50	$1,001.40