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	$94.31	8.341%	$102.1764	$102.18	$102.20	$102.20
Purchase #2	$133.52	9.657%	$146.414	$146.41	$146.40	$146.40
Purchase #3	$221.82	13.565%	$251.9099	$251.91	$251.90	$251.90
Purchase #4	$41.25	6.318%	$43.8562	$43.86	$43.85	$43.90
Purchase #5	$158.50	12.809%	$178.8023	$178.80	$178.80	$178.80
Purchase #6	$143.87	8.364%	$155.9033	$155.90	$155.90	$155.90
Purchase #7	$136.90	12.752%	$154.3575	$154.36	$154.35	$154.40
7 purchase totals =	$930.17		$1,033.4196	$1,033.42	$1,033.40	$1,033.50