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	$150.48	3.318%	$155.4729	$155.47	$155.45	$155.50
Purchase #2	$154.43	7.707%	$166.3319	$166.33	$166.35	$166.30
Purchase #3	$146.80	7.778%	$158.2181	$158.22	$158.20	$158.20
Purchase #4	$142.86	3.837%	$148.3415	$148.34	$148.35	$148.30
Purchase #5	$193.73	9.358%	$211.8593	$211.86	$211.85	$211.90
Purchase #6	$164.94	8.737%	$179.3508	$179.35	$179.35	$179.40
Purchase #7	$56.47	11.334%	$62.8703	$62.87	$62.85	$62.90
7 purchase totals =	$1,009.71		$1,082.4448	$1,082.44	$1,082.40	$1,082.50