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	$153.85	5.411%	$162.1748	$162.17	$162.15	$162.20
Purchase #2	$246.34	12.723%	$277.6818	$277.68	$277.70	$277.70
Purchase #3	$94.79	7.750%	$102.1362	$102.14	$102.15	$102.10
Purchase #4	$166.78	12.673%	$187.916	$187.92	$187.90	$187.90
Purchase #5	$182.25	9.815%	$200.1378	$200.14	$200.15	$200.10
Purchase #6	$60.69	3.667%	$62.9155	$62.92	$62.90	$62.90
Purchase #7	$13.54	9.766%	$14.8623	$14.86	$14.85	$14.90
7 purchase totals =	$918.24		$1,007.8244	$1,007.83	$1,007.80	$1,007.80