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	$116.60	5.851%	$123.4223	$123.42	$123.40	$123.40
Purchase #2	$38.66	13.663%	$43.9421	$43.94	$43.95	$43.90
Purchase #3	$117.86	11.187%	$131.045	$131.05	$131.05	$131.00
Purchase #4	$198.60	13.473%	$225.3574	$225.36	$225.35	$225.40
Purchase #5	$106.80	6.128%	$113.3447	$113.34	$113.35	$113.30
Purchase #6	$131.46	4.650%	$137.5729	$137.57	$137.55	$137.60
Purchase #7	$89.94	13.239%	$101.8472	$101.85	$101.85	$101.80
7 purchase totals =	$799.92		$876.5316	$876.53	$876.50	$876.40