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	$107.29	3.575%	$111.1256	$111.13	$111.15	$111.10
Purchase #2	$244.94	7.300%	$262.8206	$262.82	$262.80	$262.80
Purchase #3	$177.88	11.813%	$198.893	$198.89	$198.90	$198.90
Purchase #4	$108.97	9.305%	$119.1097	$119.11	$119.10	$119.10
Purchase #5	$9.97	8.231%	$10.7906	$10.79	$10.80	$10.80
Purchase #6	$38.65	11.842%	$43.2269	$43.23	$43.25	$43.20
Purchase #7	$97.54	5.458%	$102.8637	$102.86	$102.85	$102.90
7 purchase totals =	$785.24		$848.8301	$848.83	$848.85	$848.80