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	$106.71	11.641%	$119.1321	$119.13	$119.15	$119.10
Purchase #2	$29.81	7.458%	$32.0332	$32.03	$32.05	$32.00
Purchase #3	$64.69	13.372%	$73.3403	$73.34	$73.35	$73.30
Purchase #4	$128.46	13.347%	$145.6056	$145.61	$145.60	$145.60
Purchase #5	$115.81	6.342%	$123.1547	$123.15	$123.15	$123.20
Purchase #6	$187.98	5.395%	$198.1215	$198.12	$198.10	$198.10
Purchase #7	$31.78	6.321%	$33.7888	$33.79	$33.80	$33.80
7 purchase totals =	$665.24		$725.1762	$725.17	$725.20	$725.10