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	$128.63	11.414%	$143.3118	$143.31	$143.30	$143.30
Purchase #2	$112.74	10.370%	$124.4311	$124.43	$124.45	$124.40
Purchase #3	$213.38	11.639%	$238.2153	$238.22	$238.20	$238.20
Purchase #4	$54.96	13.468%	$62.362	$62.36	$62.35	$62.40
Purchase #5	$24.73	13.833%	$28.1509	$28.15	$28.15	$28.20
Purchase #6	$177.69	12.321%	$199.5832	$199.58	$199.60	$199.60
Purchase #7	$192.85	6.520%	$205.4238	$205.42	$205.40	$205.40
7 purchase totals =	$904.98		$1,001.4781	$1,001.47	$1,001.45	$1,001.50