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	$90.40	13.161%	$102.2975	$102.30	$102.30	$102.30
Purchase #2	$245.51	6.540%	$261.5664	$261.57	$261.55	$261.60
Purchase #3	$63.35	13.660%	$72.0036	$72.00	$72.00	$72.00
Purchase #4	$185.89	9.486%	$203.5235	$203.52	$203.50	$203.50
Purchase #5	$235.81	6.641%	$251.4701	$251.47	$251.45	$251.50
Purchase #6	$30.79	11.691%	$34.3897	$34.39	$34.40	$34.40
Purchase #7	$153.94	4.334%	$160.6118	$160.61	$160.60	$160.60
7 purchase totals =	$1,005.69		$1,085.8626	$1,085.86	$1,085.80	$1,085.90