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	$95.45	9.132%	$104.1665	$104.17	$104.15	$104.20
Purchase #2	$24.92	10.687%	$27.5832	$27.58	$27.60	$27.60
Purchase #3	$242.52	9.438%	$265.409	$265.41	$265.40	$265.40
Purchase #4	$33.48	13.596%	$38.0319	$38.03	$38.05	$38.00
Purchase #5	$178.46	4.468%	$186.4336	$186.43	$186.45	$186.40
Purchase #6	$137.65	12.848%	$155.3353	$155.34	$155.35	$155.30
Purchase #7	$234.81	3.687%	$243.4674	$243.47	$243.45	$243.50
7 purchase totals =	$947.29		$1,020.4269	$1,020.43	$1,020.45	$1,020.40