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	$132.92	13.197%	$150.4615	$150.46	$150.45	$150.50
Purchase #2	$220.30	12.726%	$248.3354	$248.34	$248.35	$248.30
Purchase #3	$134.80	7.415%	$144.7954	$144.80	$144.80	$144.80
Purchase #4	$82.82	3.156%	$85.4338	$85.43	$85.45	$85.40
Purchase #5	$177.73	5.864%	$188.1521	$188.15	$188.15	$188.20
Purchase #6	$68.79	5.377%	$72.4888	$72.49	$72.50	$72.50
Purchase #7	$214.55	11.151%	$238.4745	$238.47	$238.45	$238.50
7 purchase totals =	$1,031.91		$1,128.1415	$1,128.14	$1,128.15	$1,128.20