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	$101.79	3.639%	$105.4941	$105.49	$105.50	$105.50
Purchase #2	$142.70	3.233%	$147.3135	$147.31	$147.30	$147.30
Purchase #3	$238.92	5.286%	$251.5493	$251.55	$251.55	$251.50
Purchase #4	$189.73	4.527%	$198.3191	$198.32	$198.30	$198.30
Purchase #5	$63.47	3.372%	$65.6102	$65.61	$65.60	$65.60
Purchase #6	$218.50	12.509%	$245.8322	$245.83	$245.85	$245.80
Purchase #7	$192.29	8.813%	$209.2365	$209.24	$209.25	$209.20
7 purchase totals =	$1,147.40		$1,223.3549	$1,223.35	$1,223.35	$1,223.20