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	$189.61	9.863%	$208.3112	$208.31	$208.30	$208.30
Purchase #2	$38.61	5.270%	$40.6447	$40.64	$40.65	$40.60
Purchase #3	$133.42	13.524%	$151.4637	$151.46	$151.45	$151.50
Purchase #4	$62.74	9.849%	$68.9193	$68.92	$68.90	$68.90
Purchase #5	$94.88	9.618%	$104.0056	$104.01	$104.00	$104.00
Purchase #6	$219.54	6.694%	$234.236	$234.24	$234.25	$234.20
Purchase #7	$165.61	11.615%	$184.8456	$184.85	$184.85	$184.80
7 purchase totals =	$904.41		$992.4261	$992.43	$992.40	$992.30